Instant racing or historical race wagering is an electronic gambling system that allows players to bet on replays of horse races or dog races that have already been run. Here, in Kentucky the historical racing terminals resemble slot machines and are based on historical horse races.
By law they have to be called instant or historical racing machines but the average person is not going to see any visible difference. Once you select the 'handy helper' button the play is the same as a slot machine. Some of the newer machines even auto select that option for you unless you choose to over-ride it. If you can see any real difference between them and a slot machine be sure to tell me about it.
Technically speaking the internal algorithms are slightly different because the race results do affect the results. But for the average player there isn't any difference. If you enjoy playing slots, you will enjoy playing these machines.
They aren't slot machines. They are historical racing machines.