In the mobile development world, a device emulator is a desktop application that emulates mobile device hardware and operating systems, allowing us to test and debug our applications and see how they are working. There are also operating system emulators that don’t represent any real device hardware but rather the operating system as a whole. These exist for Windows Mobile and Android.
On the other hand, a simulator is a less complex application that simulates some of the behavior of a device, but does not emulate hardware and does not work over the real operating system. These tools are simpler and less useful than emulators. A simulator may be created by the device manufacturer or by some other company offering a simulation environment for developers.
Firtman has compiled a list of 37 resources for mobile device emulators and simulators. We almost never have all the resources we need for development, particularly mobile.