The Restore File command restores the current file to its original contents, as it was when it was first opened.
Reverting will lose all changes you made since it was first opened, even if you saved the file. The file that is saved on disk is not altered. Only the open file buffer is restored.
You should use caution with this command, since it effectively undoes any saving you performed on the file.
Note that you can use the Undo command to undo the Restore File operation.