In a very simple way. As the temperature increases, the pressure increases as well. For a given volume of air (say the air in a car tire) doubling the temperature doubles the pressure. Halving the temperature halves the air pressure. For this simple relation to work, it is important that you measure the temperature using special units called Kelvin. Water freezes ar 273 Kelvin, and boils at 373 Kelvin.

You asked a really good question.First, let's pretend we have a box and in that box we have some air. Now let's heat up the box. When we heat the air in the box, the air expands. A bigger volume of gas inside the box means that the pressure inside is greater. Conversely, if the temperature of the gas decreases, its volume will shrink and the pressure inside the box will go down.

Temperature and pressure are directly related. If the temperature is high then the pressure is also high and vice versa. Increasing temperature is a way of adding heat energy. So if you have a bunch of particles and you increase the temperature (or add energy) these particles start moving. When the particles are moving they will bounce into one another. This is what increases the pressure.

For example, think of a teapot of water that you are boiling. You are adding heat to the pot which will heat up the water. The water molecules start moving around and smacking into each other building up their pressure until a point where they start to evaporate (water vapor or steam) --the increased pressure and the escaping molecules are what causes the teapot to whistle. Another example for the opposite scenario (decreasing pressure leads to decreasing temperature) that I can think of: If you were to take a bottle of soda that was at room temperature, shake it, and open it; the soda would be cooler than room temperature. This is because when opening the bottle the soda (which was under pressure) there is a decrease in pressure and the gas that escapes will take the heat with it.

***This would work in a 'perfect' scenario. In everyday life there are too many other factors that may come into play which might prove this to be wrong.

Air pressure is the force exerted on you by the weight of tiny air particles (air molecules). Although air molecules are invisible, they still have weight and take up space. The molecules expand and contract as temperature increases and decreases. As the temperature increases, so does the air pressure. As the temperature decreases, so does the air pressure. There are mathematical relationships that establish the behavior of temperature, pressure, and volume. You will learn them in High School.