Pretty much as the title says. And for that matter, little omega seems pretty pointless as well. Surely they're just ways to be overly optimistic? I mean, for any positive equation I could say Big Omega is true, but it doesn't seem to actually serve a purpose. O and Theta notation make sense, however.
Thanks
The Big-Omega is reverse to O
If this is true : f(x) = O(g(x)) then it means this is also true g(x) = Omega(f(x))
By "human words" you can say - if f(x) is at most as complex as g(x), then g(x) is at least as complex as f(x)
It is something "more" than just measurment of most optimistic time for alghoritm.
PS : But for measurment of real-life alghoritms, you are basically right. You are interested in either worst case or in average case (i.e. quicksort)