Mainstage is a very powerful and flexible piece of software, and it can be complicated. However, once you can understand how its Patch concepts work, it becomes much more usable.
A patch can be a single sound, but it has far more possibilities. I tend to equate a patch with a song, where a single patch contains all the settings I will use for a song – from one to four sounds, hardware settings, and effects sends.
If Mainstage has been a mystery to you, I think this video will help a lot. You might even spot a quick cameo from a mustachioed rabbit. Enjoy!