An Option Select is a joystick or button input which functions as multiple possible actions simultaneously, letting the game engine decide the best counter to a situation. Specific instances allow only certain moves to come out, so you can worry less about your opponents options, and focus more on your own offense. 
 
In my second 3-minute fundamental tutorial (I know it's closers to 4 minutes, I really made it as short and concise as possible) I cover option selects in a general way that you can apply to any character. I go over the main archetypes of OP/SEL, such as Crouch Teching, Meaties (ground & air), and Buffering (ground & air).  Really busted my ass on the editing for this one, feedback is appreciated! Enjoy. 3-Minute Fundamentals Playlist.