MobileBet only offers 'Best Odds Guaranteed' and 'Non Runner No Bet' on selected horse-racing markets. You can find out which races and markets are included by checking Their newsletters, and the Sportsbook section of Their website.
"Best Odds Guaranteed" ensures that the price of your horse adjusts to the current market, even after your bet is placed.
"Non Runner, No Bet" means that if your backed horse pulls out, your initial stake with be returned in full.