tyre advice: folding, wire etc - what does it mean?

I am looking to buy maxxis advantages (xc version - 2.1) on crc, and don't know what the options mean. http://www.chainreactioncycles.com/Mode ... elID=12593
I think that folding are lighter, and the number is the grippiness/softness of the compound - 60a grippier than 70? Am i right?
Also are they good tyres for general xc/trail?
Thanks