Altair Inspire uses the Altair OptiStruct and SimSolid cores.
The OptiStruct core meshes the geometry to predict forces that occur by using the finite element method. It divides the smallest material thickness by 3 and creates tetra-elements, which are distributed over the design where necessary. You can refine this locally or make it coarser.
The SimSolid core calculates using the mathematical description of the geometric surfaces, so no mesh has to be made and there is no element size. This is a lot faster than meshing and is therefore particularly suitable for larger assemblies.