If you are interested in studying mathematics at university, you will encounter (pure) mathematics and applied mathematics. Roughly, applied mathematics focus on the real-world uses of mathematics. Engineering, economics, physics, finance, biology, astronomy—all these fields need quantitative techniques to answer questions and solve problems. Pure mathematics, by contrast, is mathematics for its own sake.
For more information about the differences please see the respective mathematics and applied mathematics pages or look at the modules offered in either field.