First, it depends on if the wood your cutting is dirty or clean. If it's dirty, you want to use semi-chisel chain. It cuts slower but stays sharp longer. If the wood is clean, then use full chisel (witch is what most ppl use) Round file is the most comman type of chain (it's called round file because you use a round file to sharpen it) It's alot easier to sharpen than square file, IMO. Skip chain is generally used on bars 24" and longer, it basicly has half as many teeth as full comp. Ripping chain is used for people that are milling there own boards on a mill.
For your saw, look on the bar, it should say .325 or 3/8 on it. After that it should have the number of links. 72 links for .325 pitch and 68 links for 3/8. it will have the gauge on there too. .050, .058, or .063. Yours is probably .050. good luck.
