The van you refer to is a Peugeot Boxer Professional 335, and this is simply the model and trim level of the van. In the case of the Peugeot, 'Professional' is the basic trim level and the number relates to what's known as the Gross Vehicle Weight (GVW), the '35' part suggesting it is a 3.5t van. Unless you have a need to carry particularly heavy loads then you don't need to worry too much about this, but if you've not had much experience of previous van ownership we'd advise you to look into the weight classes of different types of van to make sure they're not for the purpose you need, and to familiarise yourself with van speed limits, which are different to those of cars.