You can use the ? key in normal mode to initiate a backwards search. This is the same as searching with /, but moving through the file backwards instead of forwards.
This is useful when the string that you’re searching for contains / characters, because you don’t have to escape them in the way you would if you were doing a forward search.
Try it in the editor. Search for the string https://vimmer.io using a forward search first, and notice that it’s a bit of a pain because you have to escape the / characters. Then try searching for the same string with ?. It’s much easier!