Okay, so let's start with what accounting is: it's basically a way to keep track of money coming in and going out.
Now, there are different ways to do this in different countries, which can make it hard to compare financial information between countries. For example, in one country they might count a certain type of expense differently than in another country.
That's where the International Accounting Standards Board comes in. They make rules that tell people in different countries how to count things the same way. This makes it easier for people to compare and understand financial information from around the world.
It's kind of like if you and your friends have different ways of measuring how tall you are, but then someone comes in and says "Okay, from now on we're all going to measure ourselves the same way, so we can see who's really the tallest." The International Accounting Standards Board is that person.