You have a set of things and a set (of the same size) of other things; things and other things can be put in pairs. Given a weight for each potential pairing, find a way of pairing all the things and other things such that the weight is minimised (or maximised - but not at the same time).
Typical examples would be assigning jobs to employees, workloads to computers or rooms to housemates.
There are efficient algorithms for solving the AssignmentProblem.