Types of batteries available: AA, AAA, Ni-CD, Lithium Polymer (LiPo), Lead Acid
The most popular battery right now is LiPo Battery. It comes in different voltages. For example, 1S stand for 3.7V also known as 1 cell. 2S stand for 7.4V also known as 2 cells, 3S stand for 11.1V also known as 3 cells and so on.
A range of LiPo voltage is available - 3.7V, 7.4V, 11.1V, 14.8V, 22.2V.
Gentle reminder on usage of LiPo battery can be found here.