The purpose of the Optimizer is to analyze key performance indicators for a given process(Total execution time of process,activitiy..etc).One example usage of optimizer is to find out say what is total cost associated for a product roll out process and cost could be attributed to a key performance indicator(total execution time) and we can create multiple scenarios (best case,worst case and as-is)to simulate potential costs for the same process .If we have some historical data we can compare with one of the scenarios to identify potential process improvement steps.
--GM