Many tobaccos are compressed (flat or round) and then sliced into flakes. While flakes can often be rolled up or folded and simply stuffed (or screwed) into a pipe there are times where you might do better breaking the stuff up into finer pieces. Sometimes a flake tastes better and sometimes it burns better when it's "rubbed out" to a finer texture. If you get your hands on some flake tobak you'll figure it out in about 2-minutes.
Some flakes are pre-mangled (shredded) at the factory and they call that ready-rubbed. Some ready rub is good right into the pipe and, sometimes, it's a bit too coarse and needs to be rubbed out further by the smoker. And so on and so forth. Try some flake tobaks. They great.
