If you have found this page you are probably frantically looking for some fastboot or adb command and that's what I will give you - scroll to the end of the post and you'll find examples. For all you other people who are not freaking out about their bricked or non-booting phone...continue on. haha.
What Are fastboot And ADB
fastboot and adb are two programs found in the Android development SDK that allow you to transfer files, install programs, flash images, and run commands on your Android phone. Another thing to note: ADB can only connect to your phone while it is in recovery or booted into the OS. fastboot can only be used when your device is in bootloader mode. Finally, one of the most important things (i think) in terms of android is to access the bootloader: turn off your device and hold Power andVolume Down at the same time.