Let’s suppose you have added a post on behalf of someone else, and now you want the correct author attribution to appear when the post is published. That’s just one example of when you might want to be a ‘different’ user in the back end.
One way is to sign out and sign back in as the other person. Another way is to use the User Switching plugin. It allows you to swap between user accounts at the click of a button. You will be logged out and logged in as your desired user.
Hat tip to Chris McMahon at the Cambridge WordPress Group