To start, over/under goals markets are popular betting markets in which you bet on the total number of goals in a game. But, there are different types of over/under goals markets available, including Asian goals totals, 1st half goals totals, 2nd half goals totals, and many more varieties. Simply put, you wager that the combined score of the match will be more or less than the number offered by the betting sites.
In the traditional over/under markets, there is no possibility for a draw or refund, which is what the .5 represents. One of the most popular goals markets for betting is the over/under 2.5 goals markets, as it is often priced around evens.
Over 2.5 goals in a match mean that 3 or more goals are required to win the bet. 0, 1 or 2 goals will result in the bet losing. The over 2.5 goals market applies to 90 minutes (plus additional time) but does not include extra time.
The same principle applies to under 2.5 goals, 3 or more goals and you lose, but 0, 1 or 2 goals means you win. Also, the under 2.5 goals betting market covers 90 minutes plus additional time but does not include extra time.
However, you can also bet on the Asian totals markets, in which you can get half wins, half loses or refunds depending on the bet. For example, you can bet on over 2.0 Asian total goals, and get a refund if there are only 2 goals scored, win if there are 3+ goals scored, but lose if there are no goals or just 1 goal.