Earning is when you get money for doing something, rather than being given money, winning it or borrowing from someone else. You do the work and in return you get a reward.
Grown ups earn money for different jobs, from a firefighter to an astronaut or vet. Some jobs earn lots, some jobs earn very little – and some jobs aren’t paid at all! Other jobs only pay more if you have particular skills or are super successful, like footballers, youtubers or pop stars. Some people like getting paid for working for someone else, while others prefer to start their own businesses to earn money.