A film scanner is similar to the copier in an office. But instead of copying a printed piece of paper, it copies the negative or slide (if you're using slide film).
And instead of then sending out a sheet of paper that's a copy of the original, it creates a file for your computer.
Then, you open that file in an image editing program (such as Photoshop) and work on it: Adjust the tone, contrast and colors, crop it or whatever you like.
Time-consuming yet a lot of fun.