Anything related to finite element analysis or finite element methods (FEMs), i.e. a number of advanced numerical analysis techniques for finding approximate solutions of differential equations. FEMs are heavily used in many branches of engineering, for example to simplify the design phase of a project.
The methods transform the differential equation into a weak form over the problem domain, which is then discretized by a set of elements (e.g. a triangle-shaped plate or quadrilateral shells). This allows for a per-element approximation of the solution and an assembly of global quantities by local quadrature rules, resulting in a possibly nonlinear system of equations. For large problem statements, finding a solution might require parallel computing strategies.
Many areas of engineering profit from these techniques, e.g. solid and structural mechanics on various time- and size-scales, electrical field theory or diffusion problems, and there are plenty of (free) software solutions available. In scientific computing, users regularly need to extend the method by custom element formulations or new solution procedures, which is often done in fortran, c++ or python.
See also the Wikipedia page on FEMs.
