All terms A–Z
A
Above the foldWhatever is visible on screen before anyone scrolls, the part everyone actually sees.
Acceptance criteriaA short checklist of conditions that must be true for a feature to count as finished.
AccordionA stack of headings that each expand to reveal content underneath and collapse to hide it.
AgentAn AI that works through a multi-step task on its own, deciding what to do next and using tools along the way.
AnalyticsMeasuring how people actually use your app: visits, sign-ups, clicks, and where they drop off.
APIA defined way for one piece of software to ask another for data or to do something, like a menu with an order window.
API keyA long secret code that lets your app use another service, like a password for software.
AuthenticationHow an app checks who you are, usually by having you sign in.
AuthorizationHow an app decides what a signed-in person is allowed to see and do.
B
BackendThe behind-the-scenes part of an app that stores data, enforces rules, and does the work you don't see.
Background jobSlow work the app does out of sight after you click, so you can keep going instead of waiting.
BadgeA small rounded label or number stuck to something to flag its status or count.
BreadcrumbA trail of links at the top of a page showing where you are, like Home / Projects / Website redesign.
BreakpointA screen width at which the layout switches to a different arrangement, like going from three columns to one.
BugA mistake in the app that makes it behave differently from what was intended.
C
Call to actionThe one button or link you most want people to click on a screen, made to stand out from everything else.
CardA boxed-off rectangle that groups everything about one item, like a product, a post, or a person.
CarouselA row of slides you move through one at a time with arrows, dots, or a swipe.
ContrastHow different two colors are from each other, which decides whether text is easy to read.
Cron jobA task the app runs automatically on a schedule, like every morning at 9 or every Monday.
CRUDCreate, Read, Update, Delete: the four basic things you can do with any piece of data in an app.
D
Dark modeAn alternative color scheme with light text on dark backgrounds, easier on the eyes at night.
DatabaseWhere an app keeps its information permanently, organized so it can be found and updated quickly.
DeployPutting the latest version of your app live so real people can use it.
Design systemA shared set of colors, fonts, spacing, and ready-made components that keeps every screen consistent.
DomainYour app's address on the web, like acme.com, which you buy and point at where the app is hosted.
Drag and dropPicking something up with the mouse or finger, moving it, and letting go to put it somewhere new.
DrawerA panel that slides in from the edge of the screen on demand and slides away when you're done.
DropdownA button that opens a short list of choices when you click it, then closes once you pick one.
E
Edge caseAn unusual situation at the limits of normal use, like an empty list, a very long name, or two people editing at once.
Empty stateWhat a screen shows when there's nothing in it yet, ideally a friendly nudge toward the first action.
EnvironmentA separate copy of the app, like development or production, each with its own settings and data.
Error stateWhat the app shows when something goes wrong, ideally saying what happened and what to do next.
F
FieldOne piece of information about a thing, like a customer's email, stored as a column and often typed into a form.
File storageWhere an app keeps files like photos, PDFs, and videos, separate from its database records.
FrontendThe part of an app you see and touch in the browser or on your phone: screens, buttons, and forms.
G
H
HallucinationWhen an AI states something false with total confidence, like an invented fact, quote, or link.
Happy pathThe normal route through a feature where everything goes right: valid input, no errors, no surprises.
Hover stateHow something changes when your mouse pointer rests on it, signaling that it can be clicked.
I
Infinite scrollA list that loads more items automatically as you reach the bottom, so it never seems to end.
Inline validationChecking each form field as it's filled in and showing problems right next to it, instead of after you submit.
IntegrationA connection between your app and another product, like Slack, Google Sheets, or Stripe, so they share data or actions.
IterationImproving something in small rounds: build, look, give feedback, adjust, repeat.
L
M
Magic linkA sign-in method where the app emails you a link, and clicking it logs you in. No password needed.
Mobile-firstDesigning for the phone screen first, then expanding the layout for bigger screens.
ModalA box that appears in the middle of the screen, dims everything behind it, and needs an answer before you can carry on.
ModelThe AI engine that reads input and produces output, like GPT, Claude, or Gemini.
MVPThe smallest version of a product that still solves the core problem, built to learn fast.
O
P
PaginationSplitting a long list into numbered pages you move between with Next, Previous, or page numbers.
PerformanceHow fast an app loads and responds, which strongly affects whether people stick around.
PermissionsThe individual things a person is allowed to do, like view, edit, or delete a particular item.
PopoverA small floating panel attached to a button, opened with a click, holding a few extra options or details.
ProductionThe live version of your app that real people use, with real data.
PromptThe written instructions you give an AI model, which decide what it does and how well.
Q
R
RefactorReorganizing code to make it cleaner and easier to change, without changing what the app does.
RegressionA bug where something that used to work stops working after a change.
RelationshipHow two kinds of data connect, like one customer having many orders.
Repro stepsThe exact steps that make a bug happen, so someone else can see it for themselves and fix it.
Responsive designA layout that rearranges itself to fit any screen, from a wide monitor to a phone.
RoadmapAn ordered list of what to build next and later, so good ideas get parked instead of crammed in now.
RolesLabels like Admin, Editor, or Viewer that group what different kinds of people can do in an app.
RollbackSwitching the live app back to an earlier version when a new release breaks something.
S
SchemaThe blueprint of an app's data: which tables exist, what fields each has, and how they connect.
Scope creepWhen a project keeps growing as small extra requests pile up, until it's late, bloated, or never done.
Search and filterNarrowing a long list by typing words or picking criteria, like status, date, or price.
Seed dataRealistic fake records loaded into an app so you can see and test it before real data exists.
SessionThe period an app remembers you're signed in, so you don't have to log in on every page.
SidebarA column down the side of the screen that holds the app's main navigation and stays put while you move around.
Sign-up flowThe steps a new person goes through to create an account, from the first click to being inside the app.
Single sign-onSigning in with an account you already have elsewhere, like Google or your company login, instead of a new one.
Skeleton screenGrey shapes that stand in for content while it loads, so the page has its final shape right away.
SpecA written description of what an app should do and how it should look, detailed enough to build from.
StagingA private rehearsal copy of the live app where you check new changes before customers see them.
Structured outputAsking an AI to answer in a fixed, machine-readable shape, like named fields, instead of free text.
T
TableOne list in the database holding one kind of thing, like customers or orders, laid out in rows and columns.
TabsA row of labels that switch between different views in the same spot, like folder tabs.
ToastA small message that pops up, says one thing, and leaves on its own.
ToggleA little sliding switch for turning one setting on or off, which takes effect right away.
TokenThe small chunks of text an AI model reads and writes, which is how AI usage is measured and priced.
TooltipA tiny label that appears when you hover over or focus something, explaining what it is.
TypographyThe choice and arrangement of fonts: which typefaces, what sizes, how bold, and how tightly spaced.
U
UndoA quick way to reverse what you just did, which often replaces an "Are you sure?" question.
User profileThe information an app keeps about each person, like name, photo, and preferences, and the page to edit it.
User storyA one-sentence description of a need from the user's side: "As a ___, I want ___ so that ___."
V
Verification codeA short number sent to your email or phone that you type in to prove it's really you.
Version controlA system that saves every change to the app's code, so you can see history and go back to any earlier version.
Visual hierarchyArranging size, weight, color, and position so people notice the most important thing first.
W
WebhookA way for another service to notify your app the moment something happens, instead of your app checking repeatedly.
WhitespaceThe empty space between and around things, which makes a screen feel calm and easy to read.
WireframeA rough, boxes-and-labels sketch of a screen's layout, without colors or real content.