Most commercial walkie-talkies are not encrypted in any sense; they broadcast the signal plainly, so any similar walkie-talkie can read the signal.

A cellphone is connected to a cell tower to place and maintain the call. The cell tower encodes each cellphone's connection with a specific code to keep the data separate. A phone can only interpret the data that is encoded with their specific code; they will ignore others, so as to not generate extraneous noise on the call.