Each DSP has its own optimization algorithm. Using learned and pre-defined rules a DSP optimizes it Real Time Bidding to reach the goals defined by the marketer.
Optimize frequency and CPM to reach the maximum number of unique users
Optimize CTR to maxmize the number of clicks on the defined budget
Optimize Conversion Rates to maximize the number of leads acquired
Optimize Install Rate to maximize the number of app installs
Optimize video completion rates to maximize the number of reproductions
Optimize engagement rates on rich media ad units