Cement is manufactured through the process of grinding: blending and melting limestone, iron, silica, and shale to form a lava like substance called clinker. The clinker is then ground into the fine powder we call cement.
To get a perspective on how much cement society consumes in any given year, consider this: only water is consumed in greater quantity. Globally, roughly 4 billion tonnes of cement is manufactured annually; roughly 14 million tonnes comes from Canada.
Cement is often confused with concrete. Sometimes you'll hear the term "cement sidewalk" or "cement slab" when the product being refered to is actually concrete, a composite material. Cement is just one ingredient in the mixture that creates concrete, but it is the most chemically active ingredient and crucial to the quality of the final product. When cement is mixed together with water they form a paste that binds together sand, gravel, and various admixtures to form concrete, the most widely used construction material in the world!