Pressure is caused by the collisions of rapidly moving molecules of that make up the gas.
The higher the temperature of the gas molecules the higher the kinetic energy of the gas molecules. The more kinetic energy the harder the molecules hit each other and the outside of what ever container that they might be in. Thus the pressure is increased with an increase in temperature because each collision contains more energy.
The smaller the volume of the gas molecules the higher the pressure. This is because the same number of molecules are pushed closer together thus increasing the number of collisions. The more collisions the more pressure.
If there is an increase the number of molecules in the same volume this will also increase the pressure. Because there are more molecules in the same volume there will be more collisions increasing the pressure.