As I understand it:
Simulcasting means transmitting from more than one transmitter at the same time and all transmitters are on the same frequency. Used to saturate a small area where radio signals are soaked up due to building construction, or to cover a very large area where only one transmitter doesn't have enough horsepower to get everywhere.
Multicasting, means a dispatcher is transmitting on more than one transmitter and each transmitter is on a separate frequency. Usually, field units hear the dispatcher, but not other field units on a different frequency.
Patching, either "soft" or "hard" means two or more transmitters, each on its own frequency are connected together so that field units on one channel can hear field units on a different channel.
"Hard" patching means the patch is always turned on.
"Soft" patching means the patch is pretty much set up, all the dispatcher has to do is "flick a switch".
Hope I didn't tell you how to make a watch when you wanted to know what time it was.