Blending

got a question for chip how do you make a overlay texture and then make it blend with the original like in superstruct or in many stranded maps

Do you mean with Alpha on a displacement or with a custom texture with an invisable (alpha) background?

ehh what ? okay lets say i wanted a grass area with a bit of sand at the edges how would i do that?

Make a displacement with a texture that has the word "blend" in it. See here:
http://www.halfwit-2.com/?page=tutorials&category=19

More specifically:
http://www.halfwit-2.com/?page=tutorials&id=78

is there some kind of easy way to make terrain like in this map http://www.garrysmod.org/downloads/?a=view&id=31262

Terrain Generators can generate terrain from image files (grayscale to show height) and real-world places with certain applications/websites but it is generally frowned upon.

Yeah, the only proper way to do it is either with the SDK or by manually making a grayscale image, using generators is, as chip said, frowned upon.

If you're gonna make a grayscale, then by any means use the generator to convert it into a displacement, using your grayscale, but make sure you put time into it, and didn't just click generate a few times.