A differential cohomology theory is differential geometric refinement of a generalized cohomology theory (in the sense of algebraic topology). Examples naturally arise in physics or in the study of secondary invariants (e.g. Chern-Simons invariants). We discuss this notion from a higher categorical point of view. This leads to a natural decomposition of any differential cohomology theory which we illustrate with many examples. Moreover we show how to obtain a good integration theory and a notion of twisted differential cohomology and discuss some aspects and examples.