Venus is the second closest planet to the Sun. It is referred to as Earth's sister planet due to its similar structure, size and mass.
Although Venus is not the closest planet to the Sun (in which the title goes to Mercury), it is in fact the hottest. This is because Venus has a thick and dense atmosphere of carbon dioxide and sulfuric acid. Under the atmosphere, the temperature rises up to 475 degrees Celsius, and the pressure is equal to 92 bars.
The compounds in Venus' atmosphere are capable of reflecting light efficiently. This allows Venus to reflect back most of the light from the Sun it receives. This is also the reason Venus looks so bright in the night sky (The second brightest object after the Moon).