Asphalt and bitumen are often thought of as being one and the same thing however asphalt is quite different because it is a mixture of bitumen and fillers such as sand, grit and stone particles. It is commonly used in the construction of road surfaces.
Bitumen on it's own and in definition, is the heavy residue left over from the refinement of crude oil which is the basis of the fuels we use for most forms of transport. However most road surfaces are actually asphalt, being a combination of bitumen and mineral aggregates. Other terms commonly used to describe these surfaces are tarmac and pitch.
It is acceptable to use the terms asphalt and bitumen interchangeably.