Before going forward, I should probably define what composite means for some of the newer folks reading this. A composite image when you combine visual elements from multiple sources into a single image.
There varying reasons for making a composite. One is for lighting purposes as there are times when the desired result cannot be achieved without shooting the elements of the final image seperately. Composites allow you to create something which does not exist or did not take actually place. Another can be for safety. To get a shot of an athlete making a diving catch, you are likely going to have to take the shot several times. You don't want an athlete risk getting injured in this process so having them dive onto something like a high jump pad allows you to repeat the same process without risk of injury until you get the right shot.
Here are a few more composite images I've created for various promotional campaigns along with brief descriptions:
Hopefully that offers some insight on the how and why composites can be used. In the next piece, I'll break down the lighting and assembly for a recent promotional schedule I made for Lipscomb University.