We place command signals on the radio-frequency uplink to the spacecraft, which it receives, decodes, and acts upon. Your remote control probably uses an infrared signal with its own specially coded commands. The TV set receives them, its circuitry decodes them, and the TV acts upon them.
Most remotes can probably send more commands than that.
Cassini can recognize over a thousand different kinds of commands. They're sent by computer-control which varies the phase of the uplink, modulating it with pulses, not too unlike the way the TV remote control works. But sending the actual command signals to Cassini are the very last stage of the uplink process. First, there have to be decisions about exactly what commands to send. But if you want to set up the VCR to record your favorite show tomorrow evening, a bit of planning will be required.