Simplify the following text for a Grade 13 native English-speaking person.
Original: The most common are perigee and apogee , referring to orbits around the Earth ( Greek , gÃ , `` earth '' ) , and perihelion and aphelion , referring to orbits around the Sun ( Greek , hÄ `` lios , `` sun '' ) .
Simplified: The most common are perigee and apogee , referring to orbits around the Earth , and perihelion and aphelion , referring to orbits around the Sun ( Greek â Î Î '' Î Î Ï hÄ `` lios sun ) .