A Class 2 vehicle is a rigid truck or other large vehicle over 3,500kg. For example, fire engines, bin collection vehicles and the most widely used LGVs are Class 2 vehicles. You are not qualified to drive a Class 2 vehicle with an ordinary car licence(Category B).
To drive a Class 2 vehicle, you need a Category C, or Class 2 licence. Anyone over the age of 18, who is medically fit to drive, with a car licence, can do HGV Class 2 training to upgrade their licence.