Google is always working to improve the capabilities of Google Docs - if you see something you haven't seen before, try it and see what it does.  If you don't know what it will do and don't want to risk ruining what you've been working on, make a copy of a file and experiment in that.  To make a copy, go to File -> "Save as new copy" (or "Create a copy" for spreadsheets and "New copy of presentation" for presentations).

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