What's the difference between cement and concrete?

The basics

Cement is a binder made of various rock-like elements. Concrete is created from mixing cement, sand and rock.

Cement

Cement is a dry powder used for binding. Modern cement is usually made of ground up limestone, silicon and calcium, often with aluminum, iron and other trace elements included. Cement is used to make concrete. Today, there is a wide variety of cements used for different purposes. Cement has been around for thousands of years, at least since the Roman Empire and perhaps even earlier. When Rome fell, the secrets of making cement were also lost for more than a thousand years. In 1824, an English engineer named Joseph Aspdin patented what is called Portland cement (after the limestone on the Isle of Portland), though earlier engineers had also been working on creating various mortars similar to modern cement.

Concrete

Concrete is made of cement, sand and usually gravel, though other rocks such as limestone or granite are sometimes used. Cement normally makes up about 15 percent of concrete. Much like cement, the recipe for good concrete was lost after the fall of the Roman Empire. It wasn't until 1756 that Englishman John Smeaton is credited with re-discovering the secrets of concrete by using hydraulic lime. There were versions of concrete used earlier than Smeaton's discovery, though generally they are not considered as durable as more modern concrete.