Coupled oscillators are an example of resonant energy exchange that is an interesting topic for many students in various majors, such as physics, chemistry, and electrical and mechanical engineering. However, this subject matter is considered too advanced for freshmen and sophomores, usually because of the level of mathematics involved. Mathematical treatment of the coupled oscillator problem leads to a steady-state solution of motion, which is expressed by the superposition of the normal modes. Therefore, this paper presents a simple explanation to help freshmen and sophomore students grasp the underlying physics of the coupled oscillator problem. Among the various coupled pendulum problems, a string-coupled pendulum oscillator made using a light string, as shown in Fig. 1, is one of the easiest to construct and analyze. In addition, when compared with other coupled oscillator problems, the string-coupled pendulum oscillator problem makes it easier to understand the physical meaning of the two normal mode frequencies and how these two normal mode solutions can be superposed to yield the desired steady-state solutions for a coupled oscillator.