Bid automation puts the PPC platform’s machine learning intelligence at least partially in control of your bidding. Your campaign will begin to bid differently at each auction, based upon the mathematical probabilities (calculated from metadata) of pulling a conversion, and the estimated value of that conversion.
We cover machine learning in a blog series on this site.
Automated bidding is a quickly evolving development in the world of paid search. We have a series of articles pending about this topic, covering each type of automated bidding available on the Google and Microsoft PPC platforms.