The name "I-beam" comes from the similarity between the shape of the cross section of an I-beam and the shape of the letter “I” in the alphabet. This shape allows thicker thicknesses in the top and bottom plates than in the middle. It is usually the optimal way of using material in a beam subjected to bending loads. This means I-beams allow for a high strength-to-weight ratio, making them an efficient choice for load-bearing structures.
The shape of an I-beam provides several benefits. The thicker top and bottom plates, known as flanges, are further apart from each other than the middle section, called the web. This means  the material is mostly placed where the bending stresses are high. This design results in the flanges being able to resist more bending stress than the web, while still maintaining a relatively low weight. This distribution of material makes I-beams ideal for carrying heavy loads over long spans.
Close to upper and lower flanges are high stress areas, where most of the material is positioned.
Welded I-profile vs. hot-rolled I-profile.