Final answer:
The Git message implies that you need to temporarily save your changes using the 'stash' feature before merging, which safely stores the changes in a stack-like structure for later use.
Step-by-step explanation:
When Git says "Please commit your changes or stash them before you can merge," it is referring to the action of temporarily saving changes that are not ready to be committed to the current branch. The stash operation allows you to save your local modifications away and revert the working directory to match the HEAD commit. The changes are stored in a stack-like structure and can be reapplied at a later time, either on the same branch or on a different one, using the git stash pop or git stash apply commands.