In this talk, I will discuss some results and tools concerning equivariant D-modules, with a focus on representations of reductive groups having finitely many orbits. In particular, I provide explicit descriptions of: categories of equivariant D-modules as quivers, D-module structures of local cohomology modules supported in orbit closures, Lyubeznik numbers, Bernstein-Sato polynomials of holonomic functions, character formulas.