How to judge the capacity of lithium battery for electric tools?

We often see some wireless power tools with lithium batteries labeled as 20v2000mah and 20v4000mah, and some labeled as 99tv12800ma, 138tv16800ma and 168tv22800ma. What is the difference between the former and the latter?

Generally, 18650 cells or 21700 cells (the same as Tesla) are used as lithium batteries for electric tools. The lithium battery packs with different voltages and capacities are composed of series and parallel connection and various control and protection circuits. No matter 18650 or 21700, we can find different manufacturers. According to different explanations, the voltage label will be different. There is no mandatory specification for the time being. There are 3.6V ~ 4.2V, etc., so the common battery packs are 10.8V (12V), 14.4V, 18V (21V). The capacity is relatively objective, which refers to the continuous discharge time with a certain intensity of current, generally expressed in ah (ampere hour) or MAH (milliampere hour).