Menace is an evasion ability. A creature with menace can't be blocked except by two or more creatures. That means a single blocker is never enough: the defending player must assign at least two creatures to it, or it gets through unblocked. If they lack the creatures or don't want to spend them, the attacker deals its combat damage. The same restriction applies to a Vehicle with menace while it's a creature.
In play, menace forces awkward choices. Your opponent must either double-block one attacker, often trading two creatures for one, or let it hit. That pressure can open the way for your other attackers or make blocks unprofitable. It's a natural fit for aggressive black and red decks, where creatures with menace can chip away while the opponent struggles to stabilize.
