Cambridge Analytica is a data analysis company which acquires personal data about people from their Facebook postings and other sources. It uses this to create psychological profiles of individual people, tied to their RL identities, so that it can target them with messages which will be particularly emotionally effective on them.
If Cambridge Analytica is working for a soap powder company, those messages will be adverts (obvious or under the guise of news or posts from a Facebook Friend) to sell more soap.
During the US election, Cambridge Analytica was working for the Trump campaign.
The recently linked Beast article is reasonably good: Probe Now Investigating Cambridge Analytica, Trump’s ‘Psychographic’ Data Gurus
This is also an excellent summary (it's been amended because of legal challenges, details at bottom of article): www.theguardian.com/technology/2017/may/07/the-great-british-brexit-robbery-hijacked-democracy
Cambridge Analytica's parent company, SCL, is a specialist in psy ops.
en.wikipedia.org/wiki/SCL_Group
'Based on results, communications will be specifically targeted to key audience groups to modify behavior in accordance with the goal of SCL's client. The company describes itself as a "global election management agency".'