The three types you mentioned have different amounts of "lead" or number of incomplete threads. The bottoming tap is used to add threads to a blind hole that go almost to the bottom of the hole. The downside is that these require a lot of torque and are not a general purpose tool. The taper tap (sometimes called a hand tap), requires the least amount of pressure to cut, but leaves a lot of incomplete threads in the hole. The plug tap is in between the others in terms of number of incomplete threads. I prefer the "spiral point" style, which moves the cut chips dpwn into the hole. If you are tapping a blind hole, you will need to pick out the chips. This spiral point style excels at through holes. The most common would be a straight flute plug tap. The chips in this one collect in the flutes; you will need to "break the chips" by driving the tap forward (for let's say one turn), then then backing up. You can hear the chips break. This procedure makes for small chips that won't tend to pack into the flutes. These are just the most common and others are out there, but they wouldn't be a general purpose thing. I would recommend that you get USA, European, or Japanese taps and avoid the Chinese ones. This kind of depends on how much work you do. Good luck, I hope I have been of some help.