What is portland cement?

Portland cement is a manufactured product made in several steps. First we carefully blend limestone with shale or clay and iron to a desired chemical composition. We then grind it to a fine powder called raw meal. We feed the raw meal to a rotary kiln that is fired by coal, natural gas or another high energy fuel. The temperatures in the kiln reach about 2,800° F. At these temperatures the raw meal undergoes a chemical reaction and forms a new product called clinker. The clinker is mixed with about 5% gypsum and ground to a fine powder called Portland cement.

Is cement and concrete the same thing?

No, cement is the "glue" used to make concrete. The cement in concrete is what gives concrete its strength and durability?