Okay, so you know when you go to the store to buy some candy, and you have to give the person at the register some money? Well, that money you give them is called a "tax."
Now, imagine everyone in the whole country is buying candy (or other stuff) all the time. That's a LOT of money being exchanged for stuff. The government wants to make sure they get some of that money to pay for things like roads, schools, and hospitals.
So they made a bunch of rules for how much tax people have to pay and when they have to pay it. Those rules are called "tax laws."
When you get a job, you might notice that money is taken out of your paycheck for taxes. That's because of the tax laws too.
Tax laws can be really complicated because there are different rules for different kinds of income and different things you can deduct (or take off) from what you owe. Even adults sometimes need help understanding all the tax laws!