An astronaut is someone who is completely trained to command, pilot or remain as a member of a crew in the spacecraft. The term is (more often than not) used for professional travelers to space but now is being used for anyone who travels to space.
There are a lot of uncomfortable aspects that you need to consider before thinking about becoming an astronaut. Astronauts can face physical issues such as body fluid flowing upwards or losing bone density. Balancing in space is tough to get used to too. There are long days of work when in space ( 6 AM to 9:30 PM) . The sun sets 16 times a day while on ISS, making the sleep process disrupted. Eating can be difficult too. They have to eat stickier foods such as oatmeal as the dry foods can float in the air and contaminate the environment. They do have a choice of foods and their menu is set long before their spacecraft is schedules.
Kalpana Chawla was the first woman from India to fly out to space. Her career has been an inspiration to a lot of young minds even now. She first went to space on Space Shuttle Columbia in 1997 as a robotic arm operator and a mission specialist. She lost her life in 2003 along with 7 other crew member when their spacecraft disintegrated while entering into the Earth's atmosphere. She is awarded Congressional Space Medal of Honor and several other honors in her name. Various universities, streets and buildings are named in her honor in India.
John Young was one of the first few who had the chance to walk on the moon as commander of the Apollo 16 mission. He enjoyed longest career as an astronaut, having been sent to space shuttle missions a total of 6 times. He is the first person who is the pilot and the commander of four different types of spacecrafts - Gemini, the Apollo Lunar Module, the Apollo Command/ Service Module and the Space Shuttle.