Okay kiddo, so there are these four very big companies, kind of like superheros, who are really good at checking if other companies are doing things right with their money. They're called "Big Four Auditors" because they're the four biggest "auditors" in the whole world!
Now, when we talk about "auditing," it's like double-checking if everything adds up and if everything that was done was okay. Just like how you sometimes double-check your math homework or your mom double-checks if you brushed your teeth!
So, these Big Four Auditors do that kind of double-checking for other companies. They make sure that the company didn't make any mistakes with their money, and that they're following all the rules and laws that they need to follow. They also make sure that the company is telling the truth when they say things about their money - kind of like being a lie-detector!
It's really important for companies to have auditors like the Big Four because it helps people trust them more. Like when you do your homework and your mom double-checks it, you feel more confident that you did it right because someone else also checked it!
So that's what the Big Four Auditors do - they double-check other companies to make sure everything is okay with their money and help people trust those companies more!