What does 79 Tri mean on driving Licence?

What does 79 Tri mean on driving Licence?

restricted to tricycles 79 (3) – restricted to tricycles. 96 – allowed to drive a vehicle and trailer where the trailer weighs at least 750kg, and the combined weight of the vehicle and trailer is between 3,500kg and 4,250kg. 97 – not allowed to drive category C1 vehicles which are required to have a tachograph fitted.