Explain the drugs of Conscious Sedation for newby

Hello. I'm thrilled to be starting a new job in a private endo center and eager to learn everything I can.

I was reading the thread about the drugs and dosages used on conscious sedation and was wondering if someone could give me a quick rundown on the features/benefits/effects and maybe reasons you would choose some of the drugs e.g. demerol, propofol, fentenyl, versed, benedryl, etc.
I didn't know anyone was using demerol for anything anymore (except I used it in oncology for rigors).

Really appreciate your help.

JoAnna