Ad+ is a special kind of technology that helps websites and advertisers work together. Imagine you have a toy you want to sell, and you go to a big toy store to see if they'll sell it for you. Ad+ is kind of like a helper that connects toy sellers (websites) with toy buyers (advertisers).
When you visit a website, the website has space where ads can be shown. Advertisers want to show their ads to people who are interested in buying their toys. So Ad+ visits lots of different toys stores (websites) and figures out which ones are the best ones to show ads on.
Then, when you visit that toy store, you might see an ad for the toy you want to buy. Ad+ makes sure that the right toy sellers and toy buyers are connected so that everyone is happy - the website gets paid for showing the ad, and the advertiser gets to sell their toy to someone who wants it.