A batteries design is labeled based on what type of battery it is.
Nickel-Metal Hydride batteries (NiMH) are some of the most common, easiest, and simplest batteries to use. These are usually the battery recommended to beginners.
Lithium-Polymer (LiPo) are more advanced batteries that are much smaller and can have higher voltage and discharge ratings than NiMH batteries.
Lithium-Ion (Li-Ion) are similar to LiPo batteries but carry more energy and are easier to use.