Simulator: A simulator is used to simulate an environment with all of the software variables and configurations that will be present in the actual production environment of an application. Simulators do not try to replicate the actual hardware that will run the application in production. Simulators can be written in high-level programming languages because they merely construct software ENVIRONMENTS. For example, a car RACING game application can be thought of as a simulator as it simulates a real car race.

Emulator: An emulator does try to replicate all of the hardware and software aspects of a real-world environment. In most cases, you'll NEED to develop an emulator in assembly language to accomplish this. Emulators might thus be thought of as occupying a midway ground between simulators and real-world gadgets. For example, a car simulator racing game can be thought of as an emulator. It provides the hardware aspects of car racing as well with the help of emulators.

• Emulators replicate both hardware and software features, WHEREAS simulators solely simulate environment features that may be adjusted or created using the software. Emulators aren't a replacement for real-device testing since they don't always do a good job of simulating the hardware and software of a production system. They simply allow you to create an environment that is more SIMILAR to that of a real device.
• Emulators are somewhat slower as compared to simulators as emulators need to sense the movement of hardware devices, convert it into a digital signal, and then process them.