A battery holder is one or more compartments or chambers for holding a battery. A battery holder is a plastic case with the shape of the housing molded as compartments that accept batteries.
Coiled spring wire or flat tabs that press against the battery terminals are the two most common methods of making the electrical connection inside a holder.

This 3 x 1.5V AA Battery Holder can hold 3 1.5V AA battery which can make 4.5 V rechargeable battery pack from NiMH / NiCd cells or 9V battery pack from alkaline cells or it can also be used for one-time use and throw batteries for small DIY projects.
The battery holder puts the batteries in series so that you have 3x the voltage of an AA battery. (approx. 4.5V)

It comes with a soldered open end wire. This has 2 Mounting Holes of 3 mm which can be used to mount it.