Steel rebar, short for reinforcing bar, is a steel rod used to strengthen concrete structures. It is typically made from carbon steel and features a ribbed surface to improve its bond with concrete. Rebar is essential in construction, as it helps prevent cracking and increases the tensile strength of concrete, which is naturally strong in compression but weak in tension. Rebar comes in various sizes and grades, allowing engineers to choose the appropriate type for different projects. It is commonly used in foundations, bridges, and buildings, making it a vital component in modern construction practices.