Bilingual is an adjective that describes a person or community that speaks two languages. A bilingual woman might speak Spanish and English, and a part of town where people speak Mandarin and Polish is a bilingual neighborhood.
The prefix bi- means “having two,” and the Latin word lingua means “tongue, language,” so bilingual literally means “having two tongues.” It would be a mouthful to have two physical tongues, but luckily bilingual is for language tongues: the ability to speak two languages fluently. Bilingual is also a noun, and a person can be called a bilingual, like in the African country Chad, where the official languages are French and Arabic, and where many of the citizens are bilinguals.