An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor. One ampere of current represents one coulomb of electrical charge moving past a specific point in one second.
A milliampere hour (mAh) is 1,000th of an Ah, and is commonly used as a measure of charge in portable computer batteries. The mAh provides an indication of how long the PC will operate on its battery without having to recharge it.
See a video about calculating ampere hours: