The piece of paper issued in countries where "license" is a verb1 which authorizes you to operate a motor vehicle on the public highway.
In one such country, the UK, the minimum ages to hold a driving licence varies with vehicle type:
- 16 for mopeds, pedestrian operated vehicles and ride-on lawnmowers
- 17 for motorcycles, cars and vans under 3.5 tonnes carrying no more than 8 passengers
- 18 for light goods vehicles (3.5 tonnes to 7.5 tonnes)
- 21 for heavy goods vehicles and public service vehicles (buses and coaches to you) and motorcycles with a sidecar
There are exemptions for serving forces personnel. Before you pass a driving test the licence issued is provisional which carries several restrictions; car/van drivers must be accompanied by someone holding a full licence, motorcyclists may not ride machines over 125 cc or > 11 kW power or carry pillion passengers, all vehicles must carry L plates, and learners are not permitted to drive on motorways.
Until recently, UK driving licences did not carry the bearer's photograph or date of birth, which made them great for winding up people who demand ID on visits to the USA, assuming you didn't actually care whether you got served, of course (a propos, cf. winding up hotel staff with your UK passport, which does not carry the holder's address). A "photocard" version has now been introduced to meet EU regulations, but is only mandatory for newly issued licences; as the old paper versions do not require renewal until the user's 70th birthday, they may be around a while yet.
It is worth noting that unlike many countries, in the UK you are not actually required to carry your driving licence with you when driving; if you are stopped by the police for a check and do not have it with you, you are required to show it at a police station of your choice within three days.
1. NB that in British English license and practise are strictly verbs; the nouns are licence and practice (there is no difference in pronunciation, but cf. "advise" and "advice" if you can't remember which way round they go.)