Tip refers to the ends of the axes on a Pyraminx and related puzzles. They contain three stickers each and are solvable in 0-1 moves. Tips are similar to centers on 3x3s, in that they do not change places in relation to each other, but may be rotated. Unlike on 3x3, the tips' rotation matters.
A tetraminx is a version of the Pyraminx with the tips removed.