upon completing her education and being polished up with all the social graces, a young girl (usually about seventeen) would be "presented to Society" by her parents or guardians. This was also called her "coming-out." For the elite of Regency London, the first official event for the new crop of young ladies who "came out" each year, was to be presented to the Queen. After that, their parents would usually throw a lavish debut ball in the girl's honor, making sure to invite the most eligible young bachelors of the ton! Basically the point of all this was one big marketing strategy to "sell" the girl to Society in the most glamorous, attractive, and elegant way, in order to lure the interest of a wealthy, high-ranking male and secure for the daughter the most advantageous marriage, which would benefit the entire family.
A debutante (or deb) (French word for "female beginner") is a young lady from an aristocratic or upper class family who has reached the age of maturity, and as a new adult, is introduced to society at a formal presentation known as her "debut" or "coming out." Originally, it meant the young woman was eligible for marriage, and part of the purpose was to display her to eligible bachelors and their families with a view to marriage within a select upper class circle. This traditional event varies by region, but is typically referred to as a debutante ball.