I can sign up for a 14-day free trial Pro subscription, but I have to enter my credit card information which will bill me $119.40 for a year subscription if I don't cancel it before the 14 days is over. According to a help page on Geni, a Pro subscription permits Tree Matches and Enhanced Search, with Unlimited Media and Premium Support. That also includes access to the Geni World Tree and finding relationships to other users and historic profiles.
Note that Geni.com does not permit uploading of a GEDCOM file to populate your family information, so the user has to enter the information in fields one person at a time.
I decided to start a new account with a different email address just to see what would happen. Without signing up for the Pro subscription, I entered information about myself, my parents and one set of grandparents to see what would happen. Here is the small tree that I started as "Ronald" Seaver:
Not long after entering this data, I started getting Matches (the blue ovals) on each profile. When I ran my mouse over the oval, the colored Match icons showed up - I had 0 Tree Matches (grey), 5 Record Matches (orange) and 12 Smart Matches (green).