string chords

[rinoa_chan_]

ok, so I was wanting to try out a lil violin or guitar before I head back to college and I am trying to figure out the notes. I figured out the chord charts, but if there is a chord where you strum strings 6,4,3,2,1 and push down say strings 3,2,1, how do you skip strumming string 5?
Also- wtf do all these mean?

C major:
C minor
C 7
C m7
C maj7
C 7b5
C 7#5

etc etc etc

thankies