Picture a pendulum. Consider the point when the pendulum is hanging straight down and not moving as the constant point. When the pendulum is raised and released it moves back and forth across the original constant point. Waves act just like this. Waves are made up of repetitive patterns of back and forth movement.
People use special terminology to describe waves, their properties and characteristics.
All of these terms represent wave characteristics which are essential when waves are used to calculate variables of motion such as distance, velocity, and time. Conversion factors are ratios that allow you to interchange between variables. If you had a value in meters and wanted to know what it was in centimeters you could multiply your value by 100 and have your answer in centimeters. In this example, the words centimeters and meters represent units. Units tell others what you are describing and comparing.