Branch

A separate line of development in Git. Branches let you work on new features or fixes in isolation, without affecting the main working codebase until you're ready to merge.

Branches prevent half-finished work from breaking live features. Every professional team works on branches, understanding them helps you manage developers and review work safely.

A developer creates a "feature/checkout-redesign" branch, builds the new checkout, and only merges it to main after it's tested, the live site is unaffected throughout.