The Kinetic Molecular Theory explains the behavior of gases based on the idea that they are made up of tiny particles in constant motion. These particles move in straight lines until they collide with each other or with the walls of their container. The speed of these particles increases with temperature, leading to higher pressure when they collide more frequently. This theory also states that the volume of the individual particles is negligible compared to the volume of the gas itself. Additionally, there are no attractive or repulsive forces between the particles, allowing them to move independently. This helps to explain the properties of gases, such as their ability to expand and fill any container.