Brown stuff is organic matter which is rich with carbon. The brown stuff, which is high in carbon, acts as the fiber during composting. It is basically dead material. Brown stuff is also the material we need most of during the composting process, but it is very easy to find Some examples of "brown stuff" are: dried leaves, pine needles, newspaper, and sawdust.
Green stuff is organic matter which is rich in nitrogen. While brown stuff is the most needed material in composting, green stuff is the least needed material. Also, Green Stuff is very hard to store, since they turn rotten over long periods of time. Some examples of Brown Stuff are: grass clippings, fruits, vegetables, coffee grounds, egg shells, horse manure, and left over food scraps.