After you've mastered making repeating patterns, you may need to use them again and again for mockups or digital scrapbooking or similar. However, if you just leave every pattern you create in your patterns palette it will considerably slow down your computer when you try to run Photoshop. But reopening every jpeg tile and doing edit>define pattern is tedious. Making a pattern set that you can load when you need it is much more convienient.
*Open all of the tiled patterns you want to use and save them to your patterns palette by clicking edit>define pattern. You don't want to open and save every single pattern you've ever made all at once though. As I said before, too many patterns in the palette will slow everything down. Group them together by category i.e. Halloween or Florals or group them as collections that all fit together.