Here's a simple explanation: The Solar System consists of eight major planets, which include Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, arranged in that order from closest to the Sun to farthest. Pluto, once considered the ninth planet, has been reclassified as a "dwarf planet" and is well beyond Neptune.
Mercury, being the closest planet to the Sun, has a very short orbit compared to other planets. It completes one orbit around the Sun in just about 88 Earth days. Because of its proximity to the Sun, Mercury experiences significant temperature variations, extremely hot during the day and very cold at night.