What can emulate a fully configured PC or server?

-e-mail

-database

-virtual Machine

-proxy server

Virtual Machine is the software that act as a computer with same resources utilized by the first operating system and Emulator is also is same thing.

Explanation:

Emulator

The Software or Hardware that is used to create a virtual computer using the same resources of computer that is already works on another operating system.

Example

We have installed windows 7 on the computer. Now we need another operating system such as linux on the system at the same time. we install VM ware that is a virtual Machine to enable linux as a guest system on our windows system.