It’s a field in engineering where optimization is used to optimize a engineering design for a certain purpose (e.g. a beam for stiffness).

Topology optimization is the broader field that allows topological changes to the design (e.g. the addition or removal of nodes). These optimization’s often have a solution that first have to be interpreted by an engineer to turn it into a manufacturable design.

A shape optimization performs optimization only of certain variables of a predefined design. The splines as described here seems to fit well for describing for instance sheet metal parts or cross-sections of beams.