What is an astronaut and what they do ?

Everyone has heard the term astronaut at some point of their life. We knew that is it related to the universe and space but we don't have enough information about this full time career occupation. I wanted to ask what exactly is an astronaut and what does this job includes and what is the main purpose of Astronauts.
Everyone has heard the term astronaut at some point of their life. We knew that is it related to the universe and space but we don't have enough information about this full time career occupation. I wanted to ask what exactly is an astronaut and what does this job includes and what is the main purpose of Astronauts.