Imagine you're trying to get a job. When a company wants to hire someone, they often do some checking to make sure the person they're hiring is reliable and trustworthy. This checking is like looking into your background to see if everything you've said about yourself is true and if there's anything they should be concerned about.
Now, if they find out you've lied on your resume (like saying you have a degree when you don't) or you're not allowed to work in the country, they'll probably decide not to give you the job.
But let's say they find out you've had some trouble with the law in the past, but it's not related to the job you're applying for, and you already told them about it. They might still give you the job if they think you're right for it and that your past trouble won't cause any problems.
However, in some cases, if they find something really serious, like a criminal record for a job working with money, or with kids, they probably won't hire you because it could be risky for them.
Sometimes, if they find something they don't like, they'll give you a chance to explain. For example, if you were friends with someone who got into trouble, they might want to hear your side of the story before deciding not to hire you.
These checks are important for companies because they want to make sure they're hiring good people. And for you, it's best to always tell the truth because if you lie, they might find out, and then you won't get the job.
Checking references means they talk to people you've worked with before to get an idea of what you're like as an employee. It's like getting a second opinion to make sure they're making the right choice in hiring you.