Under 3.5 is a popular betting option in sports, particularly in soccer, where bettors wager on the total number of goals scored in a match. If the combined goals of both teams are three or fewer, the bet wins; if there are four or more goals, it loses. This type of bet appeals to those who anticipate a defensive game or low-scoring match. It adds an extra layer of excitement for fans, as they not only cheer for their team but also for a specific outcome in terms of scoring.