Sometimes you accidentally add a file to your repository that you don't want. It happens to all of us. Usually, it's not that big of a deal, but it can be a problem when you commit something dangerous, such as API keys, passwords, or other sensitive information.
So you've just come back from vacation and what to see what your co-workers have been up to? Coming back to a project after a long break? There is a little-known command in git that will show you all the commits that have happened since you left off.
Sometimes one needs to grab a copy of your source repo at a specific point in time. This is the command to do so. Update the date and branch (e.g dev) according to your needs.