At 16 one can take a theory test of road rules etc. to get what's called their Learner driver license, with which they're allowed to drive, but only under the supervision of a driver holding a full license.
Once a Learner driver has held their "Ls" for 1 year, and has had at least 50 hours of driving experience (not necessarily professional lessons, I didn't have to take any) they can take a practical driving test to get their "P1" (provisional) license.
After 1 year of having their P1 license, another theory test (called the Hazard Perception Test) is taken, which basically requires drivers to touch a computer screen when they would stop/turn/slow down in a simulated driving environment. Upon passing this test, the P2 license is obtained. The provisional license has certain restrictions such as max speed limit and legal blood alcohol level.
After 2 more years of holding their P2 license, a driver can apply for their full unrestricted license by passing a test that combines theoretical knowledge and practical driving skills.
They didn't used to have this system until the Roads & Traffic Authority realised that they could make a killing by forcing drivers to take various tests (at around $60 a pop) to climb the driving ladder :groan: