This describes the configuration of the battery pack. It tells you the cells and how these are connected: 20s: The "20" in "20s" refers to the number of cells connected in series. When cells are connected in series, their voltages add up. So, if each individual cell has a voltage of, for example, 3.7 volts, then when you connect 20 of them in series, you get a total voltage of 74 volts (20 cells x 3.7 volts/cell). 2p: The "2" in "2p" refers to the number of cells connected in parallel. When cells are connected in parallel, their capacities add up, but the voltage remains the same. So, if each individual cell has a capacity of, say, 2000 milliampere-hours (mAh), then when you connect 2 of them in parallel, you get a total capacity of 4000mAh (2 cells x 2000mAh/cell). So, "20s2p" means you have a battery pack with 20 cells connected in series to provide a higher voltage and 2 sets of those series-connected cells connected in parallel to increase the capacity.