This is a typical Lithium Ion rechargeable battery in cylindrical shape that offer 1100mAh actual capacity (although it labelled 3000mAh by the OEM). It is a very low cost solution in electronic projects or small mobile robots that do not require high discharge current. You can put 2 units together to get 7.4V (norminal) or or 3 units to get 11.1V using the 18650 battery holders.
This battery comes with an integrated protection PCB to prevent over-charge/ over-discharge.