hardtail - front shock
rigid - no shock at all ( rigid front fork, and yes people still mountain bike on these)
Full suspension : front and back suspension. Front suspension is a fork, back suspension is a shock or spring integral to the frame, built into the rear triangle.

Quote Originally Posted by ridebikeme View Post
Although it isn't cost effective, there is a possibility of changing a hardtail frame into a FS. A friend of mine is also a bike shop owner, and wanted to take a frame building class. He got the idea that he would take his favorite hardtail and make it FS. Needless to say, with a lot of work and patience, he was able to do this. His bike is indeed an awesome bike and rides really well. However, for the most part, I would agree with Irulan that it simply isn't the best choice. Although, I still in my mind tend to think that "nothing is impossible", but it certainly can be not practical
wow, that is the first time I've ever heard of something like that. Takes all kinds I guess. Most normal people wouldn't consider it.

Quote Originally Posted by Trek420
Is front suspension be lighter than an alloy fork? I think when the remodel expenses get paid off I'll look at the power train or ....
You'd have to pay a LOT of money for a light fork. Comparing rigid alloy forks to suspension forks is like comparing apples to potatoes. They are two different things.