Taxes
Taxes are a important issue to just about everyone who makes money. If you want to retire or save up to buy something, how much you pay in taxes can be almost as important as how much you earn. Even someone of a modest income probably pays at least 25% of their income to the government in taxes. If you live in a developed country other than the USA that amount is likely even higher.
European taxes are quite high by American standards. Even Canadians pay more for a stronger social safety net than Americans. Are they getting their money's worth? Most people probably think they aren't, or else they wouldn't spend so much time figuring out how to pay the least amount in taxes.
There are a wide range of subjects related to taxes, from tax law to tax strategies. There are also quite a variety in the types of taxes.