When an object is closest to the Sun in its orbit around the Sun, that is called perihelion; the farthest point in the orbit is called aphelion. The generic names (making reference to any central...
Aphelion is the point in a planet's orbit when it is furthest from the sun; perihelion is the point at which it's closest. The more general terms are apoapsis and periapsis; when discussing the Moon...
First of all, very rarely do planets orbit stars in a true circle. Planets typically orbit their star in an oval shape, called an elliptical orbit, and when the planet is closer to the star it moves...