Crumpling up a piece of paper results in the once flat page (which was essentially a single plane) forming many separate planes, each oriented differently from one another. Thus the form shading on them differs, some being lighter, some being darker, due to their orientation in space. You would essentially be picking a level of darkness, anything darker than which you'd represent as black, and anything lighter than which you'd represent as white - resulting in your different major planes being either black or white.

As to your second question, the pattern of bricks (where you've got rectangles laid out) is not a texture, but the bricks themselves - where you have some bricks sticking out more, some sticking out less, the brick material and the mortar between them having their own little bumps, scrapes, flakes, etc. - are texture, made up of forms along the simple flat surface of the wall itself.