Words are inadequate

I understand in principle, but not in execution. It's not a simple list of every 1- to 140-character permutation of all allowable characters -- it can't be, as there isn't storage on the planet for that amount of data -- and I see I can type a /search in the box at the top and start spewing out a string, and the text below follows, but beyond that.. I don't see what it's getting at.