18650 is the originator of lithium-ion battery - Japan SONY company in order to save costs and then set this standard lithium-ion battery model, of which "18" meaning the diameter is 18mm, "65" meaning the length is 65mm, "0" meaning the cylindrical shape.
Common rechargeable 18650 lithium battery, the voltage is standard 3.6 or 3.7v, fully charged can be up to 4.2v, which is not related with the volumn capacity, 18650 battery capacity from 1800mAh to 2600mAh, (18650 power battery capacity 2200 ~ 3800mAh).
The USB rechargeable battery is a new type of battery. This battery packs the world-standard USB plug into the central battery pack format. So you can use the world's billions of ports to charge. Thus eliminating the traditional charging disadvantages. People no longer need to rely on a large and clumsy charger