The answer is very simple, 10.0.2.2 is the special alias to your host loopback interface (i.e., 127.0.0.1 on your development machine). So if you have a web server hosting in your local machine, you can just access it from the emulator via http://10.0.2.2/
For more information, you can reference to emulator networking in http://developer.android.com/tools/devices/emulator.html#emulatornetworking.
If you also want to access your other development machine from the emulator, you may either modify the emulator host file, or set the emulator DNS to your own one. You can refer to my previous post How to Modify Android Emulator Hosts file