Per Trailspud's request, here is a video of me sparring on the four month anniversary of my knee replacement.
Real quick summary of Jiu-Jitsu sparring:
In the video we are start in the "guard". That is my legs wrapped around his waist. Even though I am on the bottom, I am technically in a better position because I have control of his hips. The goal in this position is to sweep (roll) him over, or submit him with a choke or joint lock. If I have my legs wrapped around one of his legs this is called "Half-Guard". I do not have as much control of him in this position but there are still many sweeps and submissions that can be done in the position.
Inversely his goal is to escape my legs and "pass" them. If he does, he can either go to side body (chest on chest but perpendicular) or full mount (sitting on the chest). You also "take the back" which is basically the same as the guard but instead of facing me, his back is to me. And then ultimately submit with a choke or joint lock. When a person "taps" that means they are admitting they are in a legitimate submission. This is how we can go 100% without injury to a joint or someone passing out from a choke.
In competition we start standing but in the interest of space (other people sparring too), we either start from the knees or in the guard. If no one gets submitted, then there is a point system.
Takedown (not seen in the video) = 2 points
Sweep = 2 points
Passing the guard = 3 points
Mount = 4 points
Back Mount = 4 points
A submission ends the match. So you could be up 20 points, get caught in a submission and lose the match.
Enjoy guys!