Help me to understand various Nitrous setups please.

Ok...I'm learning here...so help me out please.

1) What is the difference between NOS (I'll just say NOS because it's quicker than typing "nitrous") wet and dry shots?

2) What does a "60 shot" mean? What kind of measurement is that?

3) Big question: What is the difference between Direct Port and a Fogger system? To my understanding, direct port is a push-button setup, like in Fast & Furious? And a fogger is a system that just mixes NOS with your fuel at a regular, steady rate?

Again, you guys' advice is really appreciated.

- Dzur