Glossary

GitHub Actions · Reference cheat sheet

📋 Overview

Alphabetical glossary of core GitHub Actions terms for workflows, jobs, runners, secrets, and reusable automation.

🔧 Core concepts

Term	Definition
Action	A reusable unit of work published for use as a step (`uses:`).
Artifact	A file set uploaded from a job and downloadable later in the workflow.
Cache	Stored dependencies keyed for faster restores across runs.
Checkout	The common first step that clones the repository onto the runner.
Composite action	An action defined as a sequence of steps in an `action.yml`.
Concurrency	Controls that cancel or queue overlapping workflow runs.
Context	Built-in objects such as `github`, `env`, `secrets`, and `steps` used in expressions.
Environment	A named deployment target with protection rules and secrets.
Event	A repository activity that can trigger a workflow, such as `push`.
Expression	A `$\{\{ \}\}` expression evaluated for conditions, inputs, and contexts.
Job	A set of steps that runs on the same runner.
Matrix	A strategy that expands one job into many variants of inputs.
Needs	A job dependency declaring that another job must succeed first.
OIDC	Federated auth letting workflows obtain cloud tokens without long-lived keys.
Permission	Token scopes limiting what `GITHUB_TOKEN` may do.
Reusable workflow	A callable workflow invoked by other workflows with `uses:`.
Runner	The machine (GitHub-hosted or self-hosted) that executes a job.
Secret	An encrypted value exposed to workflows as an environment variable.
Service container	A Docker service (e.g. Postgres) attached to a job for tests.
Step	A single command or action invocation inside a job.
Trigger	The `on:` configuration that starts a workflow for matching events.
Workflow	A YAML automation file under `.github/workflows/`.
Workflow call	The event that allows one workflow to be invoked by another.
Workflow dispatch	A manual trigger that can accept typed inputs.
Workflow run	One execution instance of a workflow.

💡 Examples

Workflow trigger and job:

name: CI
on:
  push:
    branches: [main]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: "22"
      - run: npm ci && npm test

Matrix strategy:

strategy:
  matrix:
    node: [20, 22]
    os: [ubuntu-latest, windows-latest]
runs-on: ${{ matrix.os }}

Secrets and expressions:

env:
  API_KEY: ${{ secrets.API_KEY }}
if: ${{ github.ref == 'refs/heads/main' }}

⚠️ Pitfalls

Confusing job (runner-scoped) with step (sequential unit inside a job).
Mixing secrets (encrypted) with ordinary env vars committed in YAML.
Treating cache as an artifact store — caches are best-effort and can miss.
Equating reusable workflows with composite actions — different call sites and capabilities.
Assuming matrix failures always fail-fast the same way — fail-fast is configurable.

Glossary

Glossary

📋 Overview

🔧 Core concepts

💡 Examples

⚠️ Pitfalls

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