The next step is to create an Android Virtual Device (AVD) you can use for testing your Android applications. An AVD is an emulator instance that enables you to model an actual device. Each AVD consists of a hardware profile; a mapping to a system image; and emulated storage, such as a secure digital (SD) card. One important thing to remember about emulators is that they are not perfect.
There are some applications, such as games (which are GPU heavy) or applications that use sensors such as the GPS or accelerometer. These types of applications cannot be simulated with the same speed or consistency within an emulator as they can when running on an actual device. However, the emulator is good for doing some generalized testing of your applications.