what is the c rating?

again
Ok, the mah rating of a battery is how much it can hold.
The c rating is how fast it can safely dump out what it has.
Suppose you have a gallon of water in a bucket. You could pour all that water out of the bucket in less than a second. The bucket (loosely speaking) has a high C rating.
Suppose you have that same gallon of water in a bottle with a needle tip. Even though the bottle still holds a gallon of water, it would take you quite a while to empty it through the needle tip, therefore that bottle has a low C rating.
Suppose a battery has a 1000mah rating, and a 10c rating. That means it can safely provide (1000*10) = 10,000 milliamps (or 10 amps). A 1000 mah battery that can only provide 1 amp would have a C of 1.
Another way to look at it: You can discharge a battery in 1/C hours. If the battery has a C of 10, you can discharge it in 1/10 of an hour (about 6 minutes). If it has a C of 1, you can only safely discharge it over an hour. If it has a C of 60, you can discharge it in a minute.
It is one factor that's kind of missing from many battery specs; the issue is not just how much it holds, but also how fast you can get it out (and also how fast you can put it back in again, when charging.).