As Pogue so helpfully tells the E2 community, bilingual refers to a person who knows two languages; this may, depending on the stringency of the definition, be applied only to those who are native speakers of more than one language; it certainly requires a near-native fluency in the languages in question.
I am not myself bilingual, but have on occasion wished I was; I understand it gives one a unique cultural perspective. Also, it is supposedly easier for bilingual people to learn further languages.