Basically, they're acting as a direct middleman to companies that want to buy data/information about people. So rather than you having some data, it being used by X company, then bought from X company by Y aggregate company, sold to Z company, Datawallet collects your data directly (only the data you want sold) and then gives you the money from the sale of that data, rather than some other company (or companies).
The data you give is stripped of identifiable information and put in a pool so it isn't linked back to you. So you link stuff like your Facebook, Instagram, even debit/credit card transaction data and then it's aggregated and sold and you get paid for your data.
Their philosophy (from what I can tell), is basically that if you're on the internet, your data is being collected and sold pretty much no matter what you do, so you might as well have some control over it and get paid for that data while you're at it.