Reply to Sylenth 1 queries

Hi can you please help me with these:

In the Misc modulation section what does Modwheel, Keytrack, Step Velocity and Aftertouch mean?
Also how exactly does this section work? Like why have they given 2 modulation options under these destinations?

Also next to the piano, on the left what are those to rotors exactly used for? and also what is the pitch bend exactly and also can you tell me how to use it? Like should i automate it or what?

I'm just starting off with this. Thank you.