Concrete is an artificial stone-like (construction) material, which was used by Egyptians and Romans. As binder was usually lime or trass used.

concretetypesIt is now made with 1 part of cement, 2 parts sand, 3 parts of gravel. In volume, the ratio is 1-3-5. The water is about one-tenth of the solid particles. It is usually poured into a mold and reinforced with a reinforcement of (concrete) iron or rebar (short for reinforcing bar).
It should not freeze before it is cured, that stop the process.
It should not dry out, then you get a soft (not reacted) surface.
To prevent concrete from drying it is covered with plastic for example, or you are misting or let it stand in the formwork.
Of concrete tiles, pavers, concrete blocks, piles.. are made.

Concrete that is a bit hard, may not be moved, that breaks the existing bonds irreparable.
With a floor plate larger than 35 m2 or more than 8 meters, or a transfer to another material you need to provide expansion joints in the concrete (grinding, or a plate compressible material molded in).

Prestressed concrete is concrete where the reinforcement is prestressed and placed in the concrete under tensile force. Therefore, the concrete can carry a higher load.