The Areca nut is wrapped with "lá trầu" leaf (Betel leaf) and chewed for its exhilarating lift. Betel quids chewing has been claimed to produce a sense of well-being, euphoria, heightened alertness, sweating, salivation, a hot sensation in the body and increased capacity to work.
Just like alcohol, tobacco, coffee and sakau, Areca nut and Betel leaf are culturally-approved psychoactive drugs.
The Areca nut, by association, is sometimes inaccurately called the "Betel nut".
See the Areca nut Wikipedia article.