When tossing a coin there can only be two outcomes; heads or tails. We know that the chances of the coin to land on either heads or tails are 50% each. This equals to an odds of 2.00 for either outcome.
To calculate odds we use this formula: Odds = 1/probability in decimals. In this case, this is 1/0.5= 2.00
Now imagine you were offered odds of 2.10 on Heads and odds of 2.00 on Tails from two different bookmakers. What would you bet on?
Since the actual probability of the two outcomes is the same you should, of course, bet on the higher odds.
The odds of 2.10 is higher than what the underlying probability suggests, creating a value bet. The bigger the difference, the more profitable the value bet will be.