The individual elements (cells) that are connected in series to provide the desired voltage (Volt). For example, a "3S" battery contains 3 connected Lithium cells inside. More cells mean higher voltage and usually greater power.

The discharge rate, also known as the C-Rating, indicates how quickly the battery can safely deliver its current without overheating or swelling. The values you see refer to continuous discharge, that is, the maximum current the battery can provide steadily and safely throughout its operation without overheating. There is also burst discharge, which is the maximum "burst" of current the battery can withstand for a few seconds (usually 3-5s) to cover sudden accelerations.