Okay kiddo, so imagine if every time you played with Legos, someone came along and made you pay money for every brick you used. That's kind of like what a brick tax is.
A long time ago, there was a tax on bricks that people used to build their houses and buildings. The government wanted to make money by charging people a little bit of money for each brick they used.
If you wanted to build a big house or a tall building, you would have to use a lot of bricks, and that meant you would have to pay a lot of money in taxes. Some people didn't like this because it made building things more expensive.
Over time, the brick tax went away in most places, but it was a way for the government to make money in the past.