Why do astronauts wear space suits?

Space is an inhospitable place. In the shadow of Earth, it is extremely cold. In full sunlight, without the protection of Earth's atmosphere, it is very hot. As there is no air pressure, an astronaut's blood could boil. A space suit keeps an astronaut's body at a comfortable temperature and protects him or her from the Sun's rays. The space suit's backpack contains an oxygen supply so that the astronaut can breathe in space.