Select this option if you wish to automatically start an Android emulator of your choice before the build steps execute, with the emulator being stopped after building is complete.

You can choose to start a pre-defined, existing Android emulator instance (also known as an Android Virtual Device, or AVD).
Alternatively, the plugin can automatically create a new emulator on the build slave with properties you specify here.

In any case, the "logcat" output will automatically be captured and archived.