Question

what is perihelion and aphelion??

Answer 1

The perihelion is the point in the orbit of a planet, asteroid or comet where[& when] it is nearest to the sun. It is the opposite of aphelion, which is where [& when] the orbit of the object is farthest from the sun.
It is the opposite of aphelion, which is the point in the orbit about the Sun where the celestial body is farthest from its focus

Answer 2

the Perihelion and aphelion are the nearest and farthest point of a body's direct orbit around the sun. a parihilion is the point of a orbit of a celestial body where it is nearest to is Orbital focus generally a star. aphelion derived from apart.