The difference between the various types of rechargeable battery is in the materials they are made of.
As battery technology has progressed, manufacturers have been able to produce lighter and more efficient batteries by changing the materials they are made from.
The 3 most common types of battery found in cordless screwdrivers are:
Nickel cadmium (NiCd)
Nickel-metal hydride (NiMH)
Lithium-ion (Li-Ion)
Each have their own particular set of characteristics.