Abstract: “Stress” is a widely used concept in engineering, but it is often misunderstood and abused in many situations. In this article we first introduce the concept of full stress, and subsequently give the normal stress and the shear stress components. On this basis, all stress component information of a point is provided based on the hexahedron at that point, and the definition of the stress tensor is given. Then the concepts of principal stress, stress invariants, deviatoric stress, equivalent stress, etc., are introduced. In practical engineering applications, clarifying the above concepts and correctly applying various physical quantities related to “stress” is of great significance for structural design, structural optimization, new material research, energy development, etc.