In the garden
While you are working among the flowers, the fence breaks and needs to be fixed right away. You open a second flower bed: keep working on the flowers in one, fix the fence in the other.
In practice
git worktree add creates a second working folder connected to the same repository. Both folders share the same history (the same .git folder), but each has its own staging area and branch.
It is great for handling an urgent task without dropping what you are doing, and for letting an AI agent work in one folder while you work in the other.
Commands
git worktree add ../garden-main main # open main in another folder cd ../garden-main # go there git commit -am "Fix the fence" # commit C on main
Tip: The same branch cannot be open in two folders at the same time.