CI
Acronymcontinuous-integration, continuous integrationDefinition
Continuous integration — every change is merged into the shared branch early and often, and every merge is proved by an automated run: build, tests, lint, and whatever else the branch is gated on
The practice is the integration, not the server. A team that runs a build on every push but lets a branch age for three weeks is not doing CI; a team that merges daily and runs the suite locally, on the exact commit it pushed, is. The automation exists because integrating that often is only bearable when the check is cheap.
The discipline of not letting branches drift. Everything else — the runner, the badge, the green check — is scaffolding around that one idea.
Avoid: reading a green check as proof. A check that did not run is not a pass, and a red one can mean the runner never started rather than the tests failed. The gate is the run you can show, on the commit you pushed.