A young person acquires some legal rights at age 16. These are not the full rights of an adult, but they are the first step. (Scottish law has some differences but it is very similar.)
Briefly, 16-year-olds can drink alcohol (not spirits) with a meal in a restaurant if accompanied by an adult; join the Armed Forces with parental permission; get a driving licence for a moped; buy lottery tickets; leave home; get married with parental permission; buy a pet and take control of their own medical dealings.
Not all of these are to be recommended, of course!