i'm assuming shattering glass is a shader or texture...which one is it? what's it called? if not, how do i make shattering glass?

Texture the brush that is going to be the glass with a glass texture found under Textures/common. Then right-click on the brush (it has to be selected first) and select func/func_glass. The func_glass entity is the actual thing that makes brushes shatter in-game.