Which term describes the type of cloud an internal IT department hosting virtualization for a company would host?

When an internal IT department hosts the virtualization for a company, they are hosting a private cloud. A public cloud is virtualization infrastructure that is open to the public. An elastic cloud is a cloud that has elasticity. Rapid elasticity is one of the five characteristics that NIST defines as a characteristic of cloud computing. Internal cloud is not a term that describes virtualization; therefore, it is an invalid answer.