Across the Board

Refers to betting on a horse to finish first, second, and third to cover any of those scenarios happening during a race

Main Track Only

A horse entered for main track only (MTO) is one hoping the weather forecast or track conditions will move the race off the turf course and onto the main track. They are scratched the morning of the race if the conditions stay dry.

Tack

The equipment the horse wears, including saddle and bridle. A jockey typically has their own racing saddle, placed on each horse they ride just before the race.