We can test Plutus smart contracts using
runEmulatorTraceIO which emulates a blockchain and serves as an entry point to post transactions on it (or did I get this wrong?).
So if I can fully test my smart contracts only using
runEmulatorTraceIO why do I need the PAB ? If the PAB is necessary to interact with the blockchain, why can I test my contracts without it ?
The purpose of the PAB has not been explained in a clear way, I think. I have tried to get information from the Plutus Pioneer Programm, IOHK and other sources but I'm still confused.