The video discusses the concept of pressure in gases through a simulation. Pressure is defined as the force per unit area exerted by molecules, and increasing the number of molecules or their velocity through temperature increase leads to an increase in pressure, while decreasing them results in decreased pressure. Three ways to control gas pressure are changing the temperature, changing the number of particles, or changing the volume. If the volume decreases, the pressure increases, and if the volume increases, the pressure decreases - this is due to the frequency and force of collisions between particles and the container walls. The next video in the series explores various laws of gases.