First, your honesty "Absolute Beginner" is appreciated.

The answer to your question and most of those that will come up as you travel this new and exciting road can be found in the first 3 chapters of the "'51 bible". A couple of readthroughs will get you started and give you the basic knowledge required.

The download addresses can be found in links (look left)

Erik

PS You have already answered your question Just do a search in the "bible" or any '51 derivative datasheet on the signals you mention.