One way of understanding how people are motivated to work (and by abstraction, motivated to do things in general) can be through the consideration of Maslow’s hierarchy of needs. First published by Abraham Maslow in his 1943 paper 'A Theory of Human Motivation,' it is still a bedrock in its field today.
If you’re interested in why people are motivated to work and how you may strive to become, as Maslow put it, “actualized,” click through this gallery to find out more.