2D Elements (Area)
Area elements are two dimensional elements, these can be meshed (Finite Elements) or larger definitions which will likely be meshed later on by an analysis program, for example the outline of a floor slab.
Depending on the structural analysis program you are using, area elements can also be specified as cladding elements or load panels which do not specifically carry any specific structural properties, and are purely used as load distribution elements.
Generally structural analysis programs will have there own meshing solver (which will generally provide a better result than rhino for meshing), therefore you generally only need to define the outer bounds of a panel and set the meshing options for the programs automatic meshing routines.
Recent requests from users recently enabled for the GSA plugin have included orthotropic material generation, nomination of finite element shape acceptance criteria (warning, severe warning, all) and ability to nominate varying orientation and property assignments throughout extent of mesh.
Most structural analysis programs will only work with planar area or panel elements, therefore if you are working with a heavily curved surface it may be worth meshing the structure prior to import into the particular analysis program.
Also if you have received an already meshed model from another source the mesh convert finite elements tools provides the ability to convert Mesh from Grasshopper (it could have been generated or imported into Rhino) into finite elements with ability to triangulate quad faces failing shape checks.