I found this useful ........... How do you read betting odds? Example: Manchester United to win the League - 2/3?
Reading odds is fairly straightforward if you read them as follows:
the figure on the RIGHT is how much you bet
the figure on the LEFT is how much you win
So, using your example, if you bet 3 you win 2. All winning bets also refund your original stake, so you end up with 5.
At its simplest, you have an even money bet, this is a fifty-fity like a coin toss. This is expressed as 1/1, so if you win you get exactly what you bet, plus your stake, so you double your money.
Bets where the figure on the left is larger are called "odds against". For example, odds of 3/1 (read as "three to one") mean that the bookmaker considers it 3 times more likely that you will lose than win.
Bets where the figure on the right is larger are called "odds on". For example, odds of 1/3 (NB read as "three to one on", not "one to three") mean that the bookmaker considers it 3 times more likely that you will win than lose.