Pressure, which is the force exerted by the gas per unit area of the container, arises from the exceedingly large number of collisions between gas molecules and the container each second. The more collisions with the walls, the greater the pressure. That's why pressure increases with n, the number of moles, in the ideal gas law. Also, when the gas molecules hit the walls with greater velocity, the pressure increases. Temperature is a measure of the average velocity of gas molecules. That's why pressure goes up when temperature increases, according to the ideal gas law.
Use the sliders above to change the number of moles, temperature and volume of a gas. Observe how temperature and the number of moles affect the frequency and impact velocity of collisions with the walls, and how, in turn, the pressure is affected.