A native speaker is someone who speaks a language as his or her first language or mother tongue. Native speakers can often speak the language well since it was part of their childhood development. A native speaker's language is usually the language their parents speak and/or the language of their country of origin. It is the only language of a monolingual person, and likely the first language of a multilingual person which is acquired naturally in their native environment and which serves as the basis for their sociolinguistic identity.
Many teachers of languages are native speakers of the language they teach. This job also requires that they speak it well.