Hand taps are made in sets of three: the taper tap, the plug tap, and the bottoming tap.PLUG taps are like taper taps in that they have tapered threads at the starting end of the tap, the difference is there are fewer of them, usually the first 3-5 threads, so you get to cutting a full thread sooner..
Tapping tools are divided into four types: straight flute tap, spiral point tap, spiral fuse tap, and forming tap. Which type you use depends on what type of hole you want to thread, blind hole or through hole, and the component material.