Point object, Kinematics

I am very new to physics. This evening, I was reading about the concept of objects to be considered as point objects under some circumstances. And I was trying to think of circumstances under which the extended objects no more needed to be considered point objects. I believe I couldn't go far. Would you guys help!?

An extended object can be considered a point object or simply a particle whenever its dimensions are negligible compared to the characteristic dimensions involved in the problem and it does not have an internal structure (or it may be also neglected). For example, in studying the motion of the Earth in the solar system we can treat the planet as a point mass. Its radius is totally neglected compared to characteristic lengths such as the distance to the Sun. The Earth's fluid motions are also negligible and will not interfere appreciably in its revolution around the Sun.

An extended object can be considered a point object or simply a particle whenever its dimensions are negligible compared to the characteristic dimensions involved in the problem and it does not have an internal structure (or it may be also neglected). For example, in studying the motion of the Earth in the solar system we can treat the planet as a point mass. Its radius is totally neglected compared to characteristic lengths such as the distance to the Sun. The Earth's fluid motions are also negligible and will not interfere appreciably in its revolution around the Sun.