There is no unique set of problems which can be solved by using operations Research Models r techniques. Several operations Research Models or techniques can be grouped into some basic categories as given below.
Allocation Models: Allocation Models are used to allocate recourses to activates in such a way that some measure of effectiveness (objective function) is optimized. Mathematical programming is the broad term of the operation research techniques used to solve allocation problems.
If the measure of effectiveness such as profit cost etc, is represented as a linear functions of several variables and limitations on resources ( constraints) can be expressed as a system of linear equalities or inequalities then the allocation problem is classified as a linear function of any or all of the constraints cannot be expresses as a system of linear equalities or inequalities then the allocation problem is classified as non linear programming problems.
When the solution values or decisions variables for the problem are restricted to being integer values or just zero one values the problem is classified as an integer programming problem or a zero one programming respectively.
The problem having multiple confecting and incommensurable objective functions ( goal) subject to linear constraint is called a goal programming problems. If the decisions variables in the linear programming problems depend on chance then such a problem is called a stochastic programming problem.
If the resources such as workers machines or salesmen who can be assigned to perform a certain number of activities such as jobs or territories on a one to one basis so as to minimize total time cost or distance involved in performing a given activity then such problems are classified as assignment problems. But if the activities require more than one resource and conversely if the resources can be used for more than one activity the allocation problems is classified as a transportation problems.