What is AVD (Android Virtual Device)
An AVD is an emulator instance that enables you to model an actual device and it is used for running and testing your Android applications.
Each AVD consists of a hardware profile; a mapping to a system image; as well as emulated storage, such as a secure digital (SD) card. You can create as many AVDs as you want in order to test your applications with several different configurations. This testing is important to confirm the behavior of your application when it is run on different devices with varying capabilities.
How to create Android Virtual Device (AVD)
1) To create an AVD, select Window > AVD Manager
2) In the "Android Virtual Device Manager" dialog, click the "New..." button to create a new AVD.
3) In the "Create new Android Virtual Device (AVD)" dialog, enter the items as displayed below.
Android AVD edit
4) Click the "Create AVD" after you select desired items.
5) In this case, you have created an AVD (simply saying, an Android emulator) that emulates an Android device running version 4.1 of the OS with a built-in 10-MB SD card. In addition to what you have created, you also have the option to emulate the device with different screen densities and resolutions.
6) It is preferable to create a few AVDs with different API levels and hardware configurations so that your application can be tested on different versions of the Android OS.
After ADV has been created, it is time to test it. Select the AVD that you want to test and click the "Start..." button. The Launch Options dialog will appear.
7) Click the Launch button to start the emulator.
Tip: If you have a small monitor, it is recommended that you check the "Scale display to real size" option so that you can set the emulator to a smaller size.
8) The Android emulator will start, and after a while it will be ready for use. It will behave just like a real Android device so go ahead and try it out.