The software world
Worktree
git worktree
A second, real checkout of the same repository in its own folder, on its own branch. Not a copy you made by hand — git knows about it, both folders share one history, and switching branches in one doesn't disturb the other.
Why it matters
Part of Agent teams and parallel work → It's what makes running several agents at once practical. One agent can grind on a refactor in its own worktree while you keep working in yours, with no fighting over which branch is checked out and no half-finished edits leaking between them. It's a Power-Track tool — you reach for it the day one Claude stops being enough, and not before.
see also