Money started as a simple way for traders to trade with each other. Originally, people didn't even need money, as things were simply swapped including silver and gold. As the trade became standardized, certain number of items can be traded with certain number of other items. Value became important, as an item that was scarce or hard to get became more valued than items that were simple to obtain. This "value" became the basis of money. For example, a cow may be worth about 40 chickens. If you used this example, the value of the cow was worth more than a chicken, thus you needed more chickens to equal the value of a single cow. You can then take an arbitrary coin or bill and make a certain number of these coins and bills to be equal a chicken. Thus, instead of trading cows and chickens, people traded money. The money in the end was used to swap with the actual items. This made it easier to trade, as you no longer needed to carry around a cow or many chickens to exchange stuff.
For example, a person can help you carry stuff for a certain distance in exchange for money, which that person can eventually exchange for items. This became the basis of commerce. In old times, powerful people used slavery to get free service out of the people without paying them money. In the egyptian times, many people were enslaved to build the pyramid for the glory of the ruler. Sometimes, these slaves were killed after building the pyramid in order to keep the location of the center burial place a secret from being leaked.
Government usually are the makers of money these days. In order to get the people to be productive, everything must be negotiated via money. No longer are you able to freely pick fruits from trees to eat or hunt for animals to eat, or dig a hole in a mountain for shelter. Fruits are now on a farm or park and picking them means you are stealing. If you hunt for animals, you must get a license and pay duties. You also can't sleep anywhere without trespassing. Thus, basic survival needs are no longer free to get, and thus you are not able to survive freely like in caveman times. You must now submit to a path set out by the country designated as "successful" in order to find your food and shelter. This is usually via work, then obtaining of money.
But why are there taxes? If the government prints money, and provides these money (created out of thin air) to the banks to lend to people, then can't it simply just print enough to pay for the workers and use interest rate to rein in on inflation? Actually this is possible, but because the government is like the egyptian rulers, it wants a way to control the population. If you are taxed, you provide information on your income and also a constant loss of value to your net worth. Eventually you will run out, so you must work to make more money. This is how the colonies were controlled. They were taxed just enough so they are kept under control. Because your survival now depends on money, not free hunting, sleeping, and mountain digging, your ability to survive depends on what work you can do. Thus, you are now a slave of working, to get money, in order to survive. If you don't work, you don't get money, you don't get to live. Thus, taxes exists today as an extension of rulers controlling the population.
That is why, today, GDP is used to judge a country's progress. The gross domestic product is the value of work provided by workers. You are judged on what contribution you can provide to the total number of items or services the country produces in a certain period of time. You are forced during your most productive period (teens to middle age) to work to obtain the maximum value you can contribute. This is why old people, and people who are somehow handicapped in the system (think sick, weak, etc) are no longer valued, and is a sad victim of this system of slavery, as they are naturally unable to provide value because of their inability to work. Thus, their place in this system is to die.