docs: add description and why

README.md

@@ -2,6 +2,8 @@
 
 Quick switch between [worktrees](https://git-scm.com/docs/git-worktree) of a git repository.
 
+It preserves the path relative to the root of your repo. In other words, it's the fastest way to go from `worktree1/src/types` to `worktree2/src/types`.
+
 ### Demo
 
 https://github.com/thenbe/worktree-welder/assets/33713262/99515c17-832e-4682-913e-6d85169147df
@@ -26,3 +28,7 @@ alias ww='worktree-welder && cd $(cat /tmp/worktree-welder)'
 cd my-project
 ww
 ```
+
+### Why?
+
+https://github.com/ajeetdsouza/zoxide/issues/528