In route optimisation, a distinction is made between problems and instances. An optimisation problem is a general description of a problem (often in the form of an optimisation model). For example, the travelling salesman problem describes the problem of starting in a city, visiting all other cities and returning to the city of origin so that the distance travelled is minimised.
An instance concretises the data for a given problem so that it can also be solved. For the Travelling Salesman problem, for example, the concretisation consists of specifying the number of cities to be visited and a distance matrix (with the distances between the cities). The problem can then be solved using a suitable algorithm.