Iron is mined from the earth. In its raw form it is unrefined, not pure iron. The way to remove the iron is with heat in a process called smelting. There are three ways to process the iron into a usable form. One of them is to make steel. This is the most refined metal that can be made from iron. Most of the impurities are removed from the iron and it becomes a much stronger metal.
There are several methods to make steel. The most modern and commonly used method is with an oxygen furnace. Very pure oxygen blows through melted iron and lowers the levels of impurities. Chemicals are also added to clean up sulfur and phosphorus. At this stage, other metals can be added to create different kinds of steel. One kind of steel is called stainless steel, which is resistant to rust. Among other uses, stainless steel is used in surgical instruments.