The sun is a medium-sized star located at the center of our solar system. It is a massive, hot ball of gas, mostly hydrogen and helium, that generates heat and light through the process of nuclear fusion. The sun's diameter is about 1.4 million kilometers, which is about 109 times larger than the diameter of the Earth. Its mass is about 330,000 times that of the Earth.

In comparison, planets are celestial bodies that orbit stars and are not massive enough to trigger nuclear fusion. They are mostly composed of rock, ice, and gas, and vary greatly in size and composition. Some planets, like Earth, have a solid surface while others, like Jupiter, are gaseous giants with no solid surface.

The distance between the sun and the planets in our solar system varies greatly, with the closest planet, Mercury, located about 36 million miles (58 million kilometers) away from the sun, while the farthest planet, Neptune, is located about 2.8 billion miles (4.5 billion kilometers) away. In comparison, the nearest star to our solar system, Proxima Centauri, is located about 4.24 light-years away, which is equivalent to about 24.7 trillion miles (39.7 trillion kilometers).

In summary, the sun is a medium-sized star at the center of our solar system, while planets are celestial bodies that orbit stars and are not massive enough to trigger nuclear fusion. The sun is much larger and more massive than any of the planets in our solar system, and the distance between the sun and the planets varies greatly.