Is an air mileage reward card good for making some savings on traveling expenses?

I am not a frequent flyer; only travel for vacations or back to China.

I have a few questions. Is anybody willing to help me?

1. What's the difference between the air mileage reward credit card and those travel promotion programs offered by major airline companies? Are they compatible?

2. Which air mileage reward card shall I pick? I find the discovery miles card and Citi PremierPass Mastercard offer pretty sound terms.