Keep in mind when modifying or adding new files on different branches, if there isn't a commit, those changes will “propagate” to other branches if you switch. When you’re working on a branch and you're not quite finished but need to move onto another branch, git stash will take all the changes in your working tree and index and “stashes.” You'll run git stash apply to “unstash” the changes. Keep in mind it is applied to the current branch.

When you perform a stash, it's a merge commit. Git keeps track of the state of the index/staging-area and the working tree. Keep in mind that the index and working tree could contain changes to the same file. So essentially there are two commits when you stash. With these two commits, Git is able to “unstash” your changes.

# This command will run "apply" and a "drop" to keep your stash list clean.
git stash pop