Understanding the 5-Yard Bump in Football for Defensive Backs

Question
Hi, I play free safety in a flag football league and sometimes I am placed at corner or have to cover the slot receiver.  I'm relatively new to football but am very interested in improving myself at the safety position.  What is the five yard bump used to do and how would a DB react after the five yard bump?  When would you "bump" the receiver and when would you choose to play more loosely?  

Also (I know its alot - thanks for reading), if i am playing  the only safety position and I see a receiver on one-on-one coverage pass my position, do i backpedal to help cover him, or do i stay fixed until i see the quarterback throw the ball?

Thanks alot, appreciate it Coach

Answer
Dear Kevin,
When you are playing safety, you should not use the bump and run technique. The safeties' main responsibility is to keep all offensive players in front of him. You never want to let a receiver get behind you.

You do not jump on the pattern until you see the quarterback throw the ball. Until then keep everything in front of you.
Your friend, Coach Louis