The basic tiip is used more long range. It isn't a snap front kick/mae geri and is usually with the ball of the foot. However, there are many different types of tiips which are usually only seen in Thailand. I know that in Master Toddy's new generation, he stresses the tiip a lot to the face and he himself has an amazing one with his heel. Obviously, there are more words added these kinds of tiips but the tiip usually refers to the standard front push kick that you see in muay thai. I've even had someone tiip me in training and grab my shirt with there toes and pull me in for another short tiip.