If you have a shell model, then you can request shell membrane and/or shell bending stress results. This basically means that the stress in the shell is a combination of a tensile, or "membrane"-stress plus a bending stress, and Creo can separate these two and report the results individually. For shell elements the stress distribution through the shell is assumed to be linear. This is true for "thin", relatively flat structures.
If you are running a solid model, (more appropriate for "thick" structures), the resulting stress distribution through the thickness might not be linear. Then you can request linearized results. This means that the actual stress distribution is approximated with a linear distribution that gives the same section force/moment as the actual distribution. From this linearized stress result you get the membrane stress (i.e. pure tensile/compressive component) and bending component.
The reason (I think) for separating the stress distribution into membrane and bending components, is that norms/standards such as ASME, Norske Veritas etc, require bending and membrane stresses to be evaluated differently.
See help/support documentation for "linearized stress results" or "linearized stress query"...
