Contrary to what most people think, the gross domestic product or GDP does not tell you how much money your government made during a certain year. Instead, it tells you how much everyone generated that year combined with your country's borders, from employees who sell their time to businesses who sell products or services. All economic participants sell something and that is what the GDP measures. It basically adds up the value of all final goods and services which have been produced within a country's borders over a certain period of time. The government taxes of all of these economic participants and the money it makes each year is not the entire GDP, but rather a percentage of the GDP.
The money your government makes each year is called government revenue. But since far more people talk about the GDP, when assessing how well a country did, it should come as no surprise that the average individual tends to confuse these two terms. What you need to remember is this. Government revenue is what the government makes, whereas the GDP is what everyone within a country's borders makes combined. So, unless government officials become crazy and increase taxes to 100%, the GDP will always be greater than the government revenue.