I had a new faucet installed by a professional plumber and he made mention of these terms. The house is 28 yrs old and all the plumbing is original. Are there new standards, equipment in plumbing for the home? Advise and Thanks.

Here's a basic explain both traps serve the same purpose however since the p trap
Is vented the water that it holds to prevent sewer gasses from coming back in will not be siphoned out. The s trap however is not vented therefore vacuum can build up allowing the water to be siphoned and sewer gasses to enter the home via the drain. As far as I know s traps are no longer legal at least not in the U.S but if you already have them and they function properly I would not bother to change them. Im sure speedball can give you any details I have missed. Hope this helps

ac101 gave you a great description. Simply put, "P"traps,(see image) are vented while "S" traps,(see image) are not. The reason that "S" traps are outlawed in both the States and Canada is that without a vent it's possible for the suction of draining water to pull the trap seal down to where sewer gas can escape into your home. Hope this answers your question. Regards, Tom