A waitress is the female eqiuivalent of a waiter. Some extreme feminists and Liberals seeking to alter language and police thought wish to refer to both male and female table attendants in restaurants as waiters, as an expression of their desire to wipe all out distinctions between male and female. Some have even coined the "word" waitron to show their abhorrence of gender distinction!
The term server is now used as a "gender-neutral" term, though ironically this word derives from the gendered Latin servitor (masculine). The feminine term in Latin is servitrix.