So imagine that you're given some toys by your parents, and you need to play with them in a certain way or else you won't get any candy. That's kinda like how the government gives you rules about how to play with your money or else you might have to pay more taxes.
Mr. Druker didn't follow one of these rules and the government said he owed them more taxes. Mr. Druker didn't want to pay more taxes, so he went to a fancy court called the United States Tax Court to argue that he didn't do anything wrong.
The court looked at all the rules and how Mr. Druker played with his money, and they decided that Mr. Druker did break one of the rules, and so he did owe more taxes to the government.
In summary, Mr. Druker and the government had a disagreement about tax rules, and a court decided that Mr. Druker had to pay more taxes because he broke one of those rules.