I am talking about H1 visa. An Employer will take you on W2 basis or 1099. The diff between two is that 1) In W2 employer will cut your tax, while incase of 1099 you will be resposible for that. So, in 1099 you can show your expenses like commuting, gas etc which are exempted from tax and you might be able to save some extra bucks. Generally, in US employers goes for W2.
c2c ie. Corp 2 Corp (what I supposedly know): Suppose you are a consultant for company A which is not direct vendor for client, company B is a prime vendor for client and company B ask for candidates from company A. In that case if you are working for company B it is corp2corp