The difference between iron and steel is that iron is an element, and steel is an alloy of iron, small amounts of carbon and another material, usually another element like chromium. Iron is alloyed with other elements to make it stronger and more useful and to keep it from rusting.
There are thousands of different types of steel. The properties of carbon steel depend on how much carbon is in the steel.
Alloy steel also has carbon, but the iron is also alloyed with other elements. When chromium is alloyed with iron, it makes it harder and prevents rust. Steel with a high percentage of chromium is often called stainless steel.
When nickel is alloyed with iron, it makes it more resistant to heat and acids. Manganese makes the iron tougher and more durable, while molybdenum makes the metal stronger and more heat-resistant. Tungsten also makes the metal stronger and even more heat-resistant.
There are several ways to make steel. In the Bessemer process, molten pig iron is poured into a huge, egg-shaped converter. Then, air is blown into the converter. This causes impurities to be burned out of the iron. The converter is then tipped over, and the molten steel is poured out.