What's the main difference between a "job" and a "day job?"

Native speaker’s answer
Rebecca
A "day job" is one's regular employment, compared to a temporary or secondary job (which can be considered to be a "side job" or "night job). Generally, when most people talk about their jobs, they are talking about their day jobs. Ex: My day job is being a teacher, but I work as a writer also. Ex: I have a day job as a lawyer, but I work as a dog babysitter on the side, for fun.