Conformal invariants (conformally invariant tensors, conformally covariant differential operators, conformal holonomy groups, etc.) are of central significance in differential geometry and physics. Well-known examples of such operators include the Yamabe, Paneitz, Dirac, and twistor operators. The aim of the seminar was to present the basic ideas and some recent developments around Q-curvature and conformal holonomy. The section on Q-curvature discusses its origin and relevance in geometry, spectral theory, and physics. Here, the influence of ideas originating from the AdS/CFT correspondence becomes evident. The section on conformal holonomy describes recent classification results, its relation to Einstein metrics and conformal Killing spinors, and related special geometries.