I could help with one of them.
PDD is “Post Dial Delay”. On many countries, after you send all the digits, there is a delay or “dead air” until you hear ringing or busy.
That is the time that you will need to wait after you finish entering all the digits until you know if your call is going trought or not.
Some places are notorius for long delays, up to 15 or 20 seconds. The best known example is Cuba, where you may wait up to 25 seconds to get any indication.
About the other two terms, I will like to know too. Maybe a good old google search with the word VOIP next to it will do the trick.