Cement and concrete are not the same thing, but concrete does have cement as a primary ingredient.
In its most basic form concrete is made of cement, water, sand, and stone. Cement is a very fine powder made from limestone, sand, clay, and iron ore. In the right proportions these ingredients are crushed and super-heated in a kiln to form “clinker”. The clinker is crushed again with the correct amount of gypsum and other ingredients and the result is a fine powder that we call cement. The strength of concrete comes from the reaction between water and the chemical compounds in cement referred to as hydration. The aggregates in concrete (sand and stone both coarse and fine) serve to add volume only and are not active ingredients in the hydration process.