An ideal gas is one that is described by the kinetic molecular theory. 

Ideal gas behavior is based on a set of assumptions that simplify the behavior of gases. It assumes that gas particles have no volume and do not interact with each other. Additionally, it assumes that gas particles undergo elastic collisions, and there are no intermolecular forces present. These assumptions allow for simple mathematical calculations using the ideal gas law and make ideal gases easier to work with theoretically.

On the other hand, real gas behavior considers the complexities and deviations from the ideal gas model. Real gases have finite volumes and experience intermolecular forces, such as Van der Waals forces, dipole-dipole interactions, and London dispersion forces. These forces affect the behavior of gas particles, especially at high pressures and low temperatures when they become significant. Real gases also exhibit deviations from ideal gas behavior, particularly at extreme conditions.