Cement is a 19th century invention, it is a binder that hardens under the action of water, today most often used in the manufacture of reinforced concrete, or mortar.
It is composed of limestone and clay which, mixed with water, is taken and allows to combined sands and aggregates between them and thus constitute real artificial rocks, concretes and mortars.
Cement is a concrete constituent. It is a mixture of clay and limestone through which the different components of concrete can bind together.
The concrete is the material made from a mixture of several constituents: water, sand, gravel and cement.