Often times there is a very specific command you have entered into your bash prompt that you need to run again. You don't want to have to type it again and stepping manually through your history may be suboptimal if you typed it quite a while ago. Fortunately, there is a simple history search feature that you can use in this kind of situation.
Hit Ctrl+r and then start typing a moderately specific search term. Your
search history will be filtered by that term. Subsequent hitting of
Ctrl+r will step forward through that filtered history. Once you find the
command you are looking for, hit enter to execute it.