Total (over/under)
A total is a market on the combined score of both teams, bet as over or under a stated number.
In plain English
The identity of the winner is irrelevant. Only the combined score matters, which makes totals respond to different information than sides, such as weather, pace and injuries to scorers.
Example
A total of 47.5 goes over at a combined 48 points and under at 47, regardless of who won.
Why it matters
Totals are often priced on different information than sides, so they can offer value when a sides market is efficient.