If you're still not clear what Aggregate IQ and Cambridge Analytica were doing in the Brexit campaign there is an explainer on the BBC website HERE. Essentially, we are all characterized by five psychological traits and these can be predicted accurately by tracking your "likes" on Facebook. According to the explainer this algorithm is so accurate that after just ten likes it's better at judging your character than you or your colleagues.
With 150 likes the algorithm can determine your psychological profile better than your own parents.
Having got your profile, they know the kind of person you are and what you are likely to respond to. Hence the campaign's (for Trump and Brexit) were able to target specific ads on the news feed of these different types of people.
More than this, they knew which areas or states were crucial to winning the votes that would make the difference, and were able to deliver millions of messages repetitively at the voters likely to swing things.
But of course nobody actually knows for sure to what extent, if any, this succeeded in changing the results. Perhaps none of it had any impact but the whistle blower Christopher Wylie was sufficiently troubled by it to go public so it must have been effective. Dominic Cummings, campaign director for Vote Leave, thought enough of it to spend almost half his £7 million budget on Aggregate IQ doing similar things and claims they couldn't have done it without them.
