Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
A software emulator allows computer programs to run on a platform (computer architecture and/or operating system) other than the one for which they were originally written. Unlike a simulation, which only attempts to reproduce a program's behavior, an emulation generally attempts to model to various degrees the state of the device being emulated.
In addition to what E-design said, there are simulators and emulators for microcontrollers. The simulator allows you to test your ideas out on simulated silicon. Your circuit runs on software on a computer.
An emulator runs your code on a similar chip to the one you are designing for, but the chip is connected to computer software, so you have access to the registers in the chip. They are usually quite expensive to buy. I hope this helps to answer your questions.