Power is a Rate, Energy is an Amount

Units of measure

watts (W) – most commonly seen on light bulbs. Watts are an instantaneous rate, a measure of how fast your devices are using energy.
A 60-watt light bulb uses energy 10 times as fast as a 6-watt night-light. If you think of your battery as a gas tank, watts are a measure of how fast you are draining it at the moment.
kilowatt (kW) = 1000 watts A bigger unit

watt-hours (Wh) are a measure of quantity, the total energy used.
Watt-hours measure the watts (rate) multiplied by the time (hours) that the device was turned on. Watt-hours are the amount of “gas” you’ve got in your tank/battery or a cumulative measure of how much you’ve used. For a solar power system they’re used to measure your battery size or the accumulated energy you get out of your panels in a day or month.

watt-hours (Wh) are very often confused with watts, but they are different. Many online calculators and discussions in forums will use the term “watts” or “watts per day” when they actually mean “watt-hours” or “watt-hours per day.” For a gas powered generator watt-hours per day are directly proportional to how much gas you need to put in your tank each day.

kilowatt-hours (kWh) = 1000 watt-hours (Just a larger unit for measuring watthours.) Your monthly electric utility bill will be based on how many kilowatt-hours you used that month.

Amp-hour, or formally, ampere-hour (Ah) Is commonly used to rate battery capacity, but is totally meaningless if you don’t know the battery voltage. A 12V 100-Ah battery is twice the physical size of a 6V 100Ah battery and can do twice the work. You must multiply the Amp-hour rating of the battery by it’s nominal voltage to get it’s rating in watt-hours. Beware: You mustn’t ever use the full rated capacity of a Lead-Acid “Deep cycle” battery or you’ll soon be spending your hard-earned cash on a new one.
milliAmp-hours (mAh) are thousandths of an Amp-hour and used to rate the size of small lithium batteries in cell phones and power banks. They never state this but they use the nominal voltage of an individual LiPo cell, 3.7V, when they make up these mAh numbers. But phones charge over the 5.0V USB power connection. So a power bank rated 10,000mAh (10Ah) when fully charged contains 10Ah x 3.7V = 37Wh. On the 5V USB jack I would expect to get 37Wh ÷ 5V = 7.4Ah out of my 10Ah power bank, but in real life there are conversion losses, so even less than that!