Hi Ed, welcome to the forum...
1) Real Time Tuning works with the Roadrunner PCM which is a modified PCM modified to allow changes via USB or Bluetooth... EFILive connects to the Roadrunner and allows real time changes.
2) PID = parameter id... "PID" or "pid" has become short terminology for "parameter that can be scanned and/or logged"... other scantool vendors have the same usage.
To get an idea of how some tables interrelate, have a read of the AutoVE tutorial.
Cheers
Joe