This paper surveys complexity and approximability results for the Maximum Solution (Max Sol) problem. Max Sol is an optimisation variant of the constraint satisfaction problem. Many important and well-known combinatorial optimisation problems are instances of Max Sol: for example, Max Sol restricted to the domain {0,1} is exactly the Max Ones problem (which, in turn, captures problems such as Independent Set and 0/1 Integer Programming). By using this relationship, many different problems in logic, graph theory, integer programming, and algebra can be given a uniform treatment. This opens up for new ways of analysing and solving combinatorial optimisation problems.