Amongst the English aristocracy and landed gentry, the 'coming out' of a young woman marked her transition from child to adult, and formally signalled her availability for marriage.
Young aristocratic and upper class women were known as debutantes, and from the early 18th century onwards it was customary for them to appear before the reigning Sovereign at the start of the social season, a ritual known as 'being presented at court'. The last presentations occurred in March 1958, prior to the abolition of the practice by Queen Elizabeth II.
The social season was the period between Easter and August 12th (the start of the grouse-shooting season) when a series of social events took place where debutantes might be seen in public. Apart from balls and dinner parties, some of the most important events were (and, indeed, still are) Royal Ascot, the Henley Regatta and the Chelsea Flower show.