An I Beam, also known as a rolled steel joist (RSJ) or universal beam, features a cross-section shaped like the capital letter "I". It consists of two horizontal flanges and a central vertical web. This configuration makes the I beam excellent at handling shear and bending forces, making it ideal for structural frameworks.

I Beams are widely used due to their efficient material use and ability to support high loads with minimal steel. They’re produced in various dimensions and grades, depending on the structural demands of a project.