Is GMW different from Secret Sharing?
They are very different. GMW is a multi-party computation protocol while secret sharing is a technique to distribute a secret. GMW uses secret sharing as a building block but it also uses other primitives like an oblivious transfer (OT). GMW deals with the problem that multiple parties jointly compute a function (over their inputs) securely without revealing anything else except the final output value of the function. Note that a simple difference is that GMW does not have a particular secret distributor (well actually every party distributes secrets), as opposed to secret sharing.