I will give 4.
(1) Linear Programming (LP)- LP is a method used to optimize linear objective functions subject to linear constraints.

(2)Integer Programming (IP) - IP extends linear programming to problems where some or all decision variables must take integer values.

(3)Dynamic Programming (DP)- DP is used to solve problems that can be broken down into smaller subproblems.

(4)Network Analysis - Network analysis methods, such as Critical Path Method (CPM) and Program Evaluation and Review Technique (PERT), are used for project scheduling and management.

The difference in their applications, with some focusing models like linear programming and others on  elements like simulation.

Methods of Operational Research include linear programming, integer programming, dynamic programming, simulation, and network analysis. The key differences among these methods lie in the types of problems they address, such as whether decision variables are continuous or discrete (linear vs. integer programming), whether time and stages are considered (dynamic programming), or whether they model uncertainty (simulation).