Short answers, pulled from the story.
A tax is a mandatory financial charge imposed on an individual or legal entity by a government to support government spending and public expenditures, or to regulate economic activity by mitigating negative externalities. Governments use the revenue to fund infrastructure, military, education, public health, law enforcement, and the operation of government itself.
The first known system of taxation was in Ancient Egypt around 3000 to 2800 BC, during the First Dynasty of the Old Kingdom. The earliest and most widespread forms were the corvee, which was forced labor, and the tithe, with the Pharaoh conducting a biennial tour of the kingdom to collect tithes.
Taxes are classified as either direct or indirect and include income tax, corporate tax, capital gains tax, wealth tax, property tax, inheritance tax, sales tax, value-added tax, excise duties, tariffs, and poll taxes. An ad valorem tax is based on the value of a good or property, while a per unit tax is based on quantity regardless of price.
A progressive tax is structured so the effective tax rate increases as the taxed amount increases, while a regressive tax is one where the effective rate decreases as the amount increases. A proportional tax holds the effective rate fixed, and a lump-sum tax, such as a poll tax, is effectively regressive because lower-income people pay a higher share of their income.
The introduction of a poll tax in medieval England was the primary cause of the 1381 Peasants' Revolt. Centuries later, the Community Charge poll tax was tested in Scotland in 1989 and in England and Wales in 1990, and the shift to a single-rate tax regardless of ability to pay led to widespread refusal to pay and the Poll Tax Riots.
Among high-income countries, Denmark has the highest tax revenue as a share of GDP at 47%, while Kuwait has the lowest at 0.8%, reflecting its strong oil revenues. The global average is around 19%, with high-income countries near 22%, middle-income countries at 18%, and low-income countries at 14%.
In The Wealth of Nations, Adam Smith wrote that good taxes meet four criteria: they are proportionate to incomes or ability to pay, certain rather than arbitrary, payable at times and in ways convenient to the taxpayer, and cheap to administer and collect.