Short for hobby horse; a wooden or wickerwork toy made to be ridden just like a real horse (which was sometimes called a "Hobby"). From this came the expression "to ride one's hobby-horse", meaning "to follow a favorite pastime", and in turn, hobby in the modern sense of recreation.
A hobby is practiced for interest and enjoyment, rather than financial reward. Examples include collecting, creative and artistic pursuits, making, tinkering, sports and adult education. Engaging in a hobby can lead to acquiring substantial skill, knowledge and experience. However, personal fulfillment is the aim. People enjoy participating in competitive hobbies such as athletics, hockey, tennis etc.
What are hobbies for some people are professions for others: a chef may enjoy playing computer games as a hobby, while a professional game tester might enjoy cooking. Generally speaking, the person who does something for fun, not remuneration, is called an amateur (or hobbyist), as distinct from a professional.