Ideal gas is only a term used to represent when we are assuming the behavior of a gas fits the principles of an ideal gas, so in reality all gases are real gases and when we use the term ideal gas when we are doing calculations . The difference between the two is that when looking at ideal gases the equations used assume that 1) gases occupy a negligible fraction of the total amount of gas and 2) The interaction between the individual gas molecules with each other is negligible. These two assumptions cause a difference between real and ideal gases, since gases in real life do in fact take up space and have intermolecular interaction.