Media Optimizer provides a consolidated view of how your media is performing, along with tools to both accurately forecast and continually optimize your media mix to deliver peak return on your investment.
It's main component is Audience Management. You can read up more about it here
AAM a data management platform that helps you build unique audience profiles so you can identify your most valuable segments and use them across any digital channel.
Documentation Link:- https://marketing.adobe.com/resources/help/en_US/aam/
Introduction Link:- http://www.adobe.com/marketing-cloud/data-management-platform.html
I hope this would be of some help to you.
Thanks and Regards