The above is called Madison aka 6day racing. Original an a American from of tracking started at Madison Square Garden in NYC. They rode for 6 days 24 hrs. You sling your partner and he rides for a certain amount of laps and when he is done you come in a do the same. This was the high light when Cycling was the top sport in the ol USA. In Europe they still do this during the winter months and is really big.
Here in the US Dale Hughes and Rick Denman kept this alive in the US!IMHO.
Pursuits is riders on the opposite side of the track and they ride a prescribe amount of laps (now men do 4000 meters and ladies 3000 meters. for team pursuits they are different ones from Assie style, italian style etc.
The rider waiting to enter the action idles at the top of the track. As their partner starts to come by, they pick up speed coming down the bank. Their partner catches up and passes by them, grabbing their hand in the process. At an arms length, the current rider who is traveling faster than the rider entering the relay slings the new rider up to speed.
sounds like a sprint, the idea being you get to the line first no matter how slow or fast you go. Most sprints start slow as you cannot sprint for 3 whole laps at 70km/h and so tactics plays a big part. Sudden bursts of speed are used to gain a gap on your opponent.
The Madison is fun to race, very hard though. The speeds are insane. Basically you ride as a team and swap out laps so that you can have rests. This means that the speed is higher than if you rode it yourself the whole way. No set changeover times, it's up to each team to change when they want to. Very tactical and demanding racing over a lot of laps.