How does Calorie work, does it make you fat, and what is the recommended daily calorie intake?

What is the recommended daily calorie intake for a 25 year old guy?

And do I have to burn off all the colories that I eat in a day, in order to not gain any weight?

For example, if I eat 1500 calories in a day, how much of it do I have to burn off in order to not gain any weight?

Thanks.