What does "odds on favorite" mean?

Question

I've heard that term before, but what exactly does it mean?

Answer 1

"odds on favorite" means that the horse is less then even money.  

For example a horse that is 2-1 is a "favorite"

but...

A horse that is 4-5 is an "odds on favorite".

It is a favorite who is less then even money.

Answer 2

the horse with the lowest odds for xample curlin was even  money so he was the odds on favoriteor  the most likely canidate to win based on the betters