Mine just has the frequency but it has privacy channels???
Okay... Get ready for the geek-speak.
Frequencies are just that. Frequencies. Like on your FM radio. 95.5, 97.1, etc. Our frequencies are in the 460 MHz UHF band. 462.525, 462.550, 462.575, etc. (Those are not the exact frequencies, but you get the idea. If anyone wants the exact frequencies, I can dig them up. I've actually programmed a couple of salvaged walkie-talkies for FRS channels, for a friend of mine.) But they're mostly all set up the same. Ch1 on a Motorola radio is Ch1 on a Midland radio, and is also Ch1 on a Kenwood radio, etc. (There are a very few exceptions, but mentioning them here will just be confusing.)
Sub-channels are not actually channels. Here's how they work...
A sub-audible (low frequency) tone - or sometimes a digital code - is transmitted along with the radio signal. Receivers set to that same sub channel will decode that tone, or code, and open up to let the transmitted audio through. Radios set to a different sub channel will sit there, and not make a peep. This is so you don't have to listen to other peoples' conversations.
What must be remembered, is that if someone is on your frequency, but using a different sub-channel, THE CHANNEL IS STILL IN USE, AND IS UNAVAILABLE FOR YOUR TRAFFIC. That's what the "monitor" button is for. Press it to make sure that nobody is using the channel, before transmitting.
Now... using sub-channel 0 effectively eliminates ALL sub-channel protocols. (In radio jargon, it's called "carrier squelch".) It's kind of like an "all-call". If there is a signal present on your main frequency, on ANY sub-channel, you will hear it.
Since we frequently use these radios waaay out in the sticks, and there are (hopefully) not a lot of other people using them, on the came channel, I find this to be the most foolproof method. We'll hear anything that's on the channel (which is fairly unlikely) but we'll also hear each other, without a lot of confusion.
Oh yeah... if you've got an old police scanner that receives UHF (which most of them do) they can be programmed for the FRS channels. No problem.
Another edit - As far as the sub-channels...
Motorola calls the technology "Private Line" or just "PL". The newer version - with the digital code - is called "Digital Private Line" or (you guessed it) "DPL".
Which is all probably TMI.