ADB Question - Pls Help

[Maddy30]

Hi Friends,
When I type adb devices the output is like this:
List of devices attached
Emulator-5554 device
0123456789ABCDEF device
After this I type adb shell then the output is like this
More than one devices/emu .
Pls help. Thanks in advance.

 

[Mustang02]

select which device you want:

adb -s {device serial} shell