Default Bid for Adwords is the price which you are willing to pay in ad group level. For example, when you want to start a new ad group in a campaign, Adwords will always ask you to enter your default bid for your new ad group. This is because if you forget to add in bid price for a new keyword in the ad group, the default bid will come into play.
With the default bid running, you are sure to show your PPC ad for that particular keyword, unless it is below bid or you have paused the keyword…