There is one secret driver every day, the same for everyone. Every name you try gets a rank: the secret is number 1, and the lower your number, the closer you are. The rank comes from a formula over each driver's real record, so two people who try the same name get the same number.
Two drivers are alike if they share a country, teams, an era and team-mates, and if their records look alike. Team-mates only count when they raced at least ten Grands Prix together in the same team: with fewer, a stand-in who did two races ended up resembling half the grid. Records are compared on a logarithmic scale, because going from zero to five wins says far more than going from fifty to ninety.
You get three. Each one shows you the driver halfway between your best guess and the secret: if the closest you have got is rank 40, the hint is rank 20. It never gives the secret away; if halfway lands on 1, you get the next one.
When you get it you see the list of the closest drivers and why they are close. That is where you learn something: who shared a garage with whom, or which driver from another decade had an almost identical career.
What the simulator says about what you have just played, measured over thousands of seasons.