Operations research, also known as management science, is the use of mathematical modelling to formulate a decision-making problem, and the use of optimization to find optimal or near optimal solutions to the problem.

This definition covers a very wide variety of problems. I am familiar with those involving combinatorial optimization. This includes resource allocation (e.g. job scheduling, bin packing), logistics (e.g. vehicle routing, facility location) and network analysis problems. I have written a master's thesis on this topic.