Bluetooth is just a way to hook up your phone to the radio. You can make calls through your phone, by using your car. Basically like putting it on speakerphone, but you use voice-commands to begin a call. You push the button on the steering wheel to prompt the car, and then you say "Call Jeff" and your car would find his phone number in your phone and call him.
OnStar minutes are minutes that you can buy to use with OnStar. Let's say you're driving around in some totally random area, and you need to call home and tell someone that you left the coffee pot on and they need to turn it off. BUT, your cell phone is dead, or you don't have reception. You can use your OnStar connection and minutes to make a phone call. Your OnStar service gives you your own "OnStar phone number," so people can even call YOU on it if you give them the phone number. That's kind of like having a pre-paid phone for emergencies. Whenever you pick up your car, they help you set up your OnStar trial and while doing that, the OnStar rep will ask if you want to buy those minutes.
Personally, I did not buy any minutes, and I'm glad I didn't. My OnStar trial ends tomorrow, and I've never wanted to or needed to use OnStar to make a phone call. But, to each his own. Some may find it handy as an "emergency" option, but I didn't because I don't plan on keeping OnStar.
**As a side note on this thread, does anyone know if OnStar offers you a super awesome amazing price if you wait as long as possible to renew? They've only offered me the standard price so far. I've considered renewing it for the next year only, since my husband is gone for the next year, just for a little more security, but I don't want to pay $20/month for it. Just wondering if you get a better deal after your trial expires, because you do with the XM radio.
They never offered me any deals other then the first offer. I told the lady if she could show me how to get the vehicle into the motel room with me so I could make calls from there I'd take their service.