Both to Score (abbreviated BTTS) is a football betting market with two outcomes: Yes (both teams score at least one goal each) or No (at least one team fails to score). The identity of the winning team, the match result, and the exact score are all irrelevant — only whether each team has scored counts.
The market settles on 90-minute goals only. Goals scored in extra time or penalty shootouts do not count. A match ending 0-0 is BTTS No. A match ending 1-1, 2-1, or 3-2 is BTTS Yes. A match ending 1-0 or 2-0 is BTTS No (one team failed to score).
Analytical approach: calculate each team's "failed to score" rate and "failed to keep a clean sheet" rate separately. BTTS Yes requires both teams to score, so you need both teams to have a low "failed to score" rate. BTTS No requires at least one team to fail — either the home or away team's defensive solidity or the opponent's weak attack makes this likely.
Combining markets: Both to Score Yes + Over 2.5 Goals is a popular double that requires at least 3 goals with both teams contributing. It pays better odds (typically 2.5-3.5) than BTTS Yes or Over 2.5 alone, and is suited to matches where you expect an open, free-scoring game.
Example
Southampton vs Brentford. Both teams score in 65% of their respective matches. BTTS Yes is priced at 1.75 (57.1% implied). Statistically, both teams failing implies independent probabilities: both score ≈ 0.65 × 0.65 ≈ 42% when defensive records of each team are taken into account. Research the combined rate carefully before placing.