I Dont Really Understand “Override Bids”?

I am currently setting up my first ad campaign using the Digital Point advertising and I am not sure about the section that asks for what do I want to set the Override Bid. Do I have to set this? or can I leave it blank? If I set a override bid, will the impressions I get not just always cost this? meaning the original bid amount I set wont matter? Can someone please give me some info about the "Override Bid" Feature? Thanks!

See original post by Sean101