The term 'Early Prices' normally applies to horseracing. Early prices are the fixed odds prices that your online bookmaker offers before the Board Prices / Live Shows come through from the racecourse.
Early Prices are provided by your online bookmaker to allow you to take a price on a horse in the morning of a race. Early Prices are usually available from around 10am through to 20 minutes before a race starts.
In the 10 minutes or so before a race starts the prices on offer are the Board Prices, which reflect the real-time state of the racecourse betting on that race.
Online bookmakers can not guarantee to offer Early Prices on every race but they try hard to price up as many races as possible on a daily basis.