The three factors that affect gas pressure are the number of gas molecules, the volume of the container and the temperature of the container that contains the gas. If there are two equal-sized containers, and one contains double the amount of gas molecules, this container has a higher gas pressure.
If the same amount of gas is in a small container, a medium container and a large container, the small container has the highest gas pressure while the largest one has the lowest gas pressure. A smaller container exerts more pressure on the gas.
When a container is heated, the molecules move faster due to the extra energy. This results in a higher gas pressure. Molecules are slower at a cold temperature, resulting in a lower gas pressure.