Details and such

Since most of the 3d programs i have used pretty much give you all the detail options needed to get textures to look more real, I'm somewhat confused on the brushes angle of constructor.
What i need or what I would like to find (did a search already) is the following explained a bit better.

How do you pump out detail in textures?

Whats the difference between a structural brush and a detailed one?

Is there any smoothing options or will there be any in the future for curves? This may be more engine based.

Basically, thats it. Just some simple questions that I'm not finding answers for very easily.