This video shows how to boot the Samsung Galaxy Exhibit t679 in recovery mode. From recovery mode you can do a factory reset which comes in handy if:
1. Your phone is stuck in boot loop
2. You forgot your screen lock password
3. You are selling the phone and are worried about your data.
Once in recovery mode you can also install CWM or Clockwork Mod which will enhance your recovery capabilities and is usually first step in rooting the phone.
Check this video for instructions on how to install CWM:
• How to Install CWM - Samsung Galaxy E...