What is a Load Bank?

Are you referring to an electrical service loan bank perhaps? I would have to agree with EUPORIUM that they are not typically mean but at times can become a bit flake.

There are different types of load banks. Here is a description that took me nearly 30 seconds to "borrow" from the web:

A load bank is a device which develops an electrical load, applies the load to an electrical power source and converts or dissipates the resultant power output of the source.

The purpose of a load bank is to accurately mimic the operational or "real" load that a power source will see in actual application. However, unlike the "real" load, which is likely to be dispersed, unpredictable and random in value, a load bank provides a contained, organized and fully controllable load.

Consequently, a load bank can be further defined as a self-contained, unitized, systematic device that includes load elements with control and accessory devices required for operation.

Whereas the "real" load is served by the power source and uses the energy output of the source for some productive purpose, the load bank serves the power source, using its energy output to test, support or protect the power source.

Next time try google if you can before you ask something like this, a small amount of knowledge when you ask a question will make you seem much more intelligent. And if this is homework...don't ask here again until you graduate.