The mAh specification of a battery stands for milliampere-hours and is the amount of milliamperes that a battery can provide to your device in an hour.
So, a battery showing specification of 1,900mAH can provide 1,900mA (milliamperes) for 1 hour of time and, in general, the higher the number, the more power the battery can store and provide over a longer period of time.
3000mAh- Up to 1 charge
6000mAh- Up to 2 charges
10,000mAh- Up to 3 charges