Breaking down raycast

Ive been working on adding guns to my FPS but i hit a snag with using the RaycastHit. Can anyone explain the syntax to me? The resources page is helpful but fails to explain anything on it. Thanks!

Resource page can be found here

this is the one you shd be looking at i guess Unity - Scripting API: Physics.Raycast

Thanks for the speedy response Flamy! This page his considerably more detail.