A power over ethernet switch could be described as an ethernet switch that as well as sending information through ethernet cables, also sends power. This is great as the need for an extra power supply for your end point device is therefore removed. The reduction in cables is usually a good idea as messy cables are a housekeeping nightmare.
The Power over ethernet switch is usually used with devices like IP surveillance devices and VOIP phones. A poe switch with 96 ports or more is not uncommon in a large company, but many small ones may use a 4 port to twenty four port unit.
These extremely functional network accessories can be bought on the internet reasonably inexpensively for the small units. Always be sure to verify that the unit you are picking is suitable for your purpose and allows for system expansion.