Ensemble forecasting has become an established part of many weather forecasting activities and is gaining ground in related areas as well. Recognizing the need for ensemble forecasting, in March 2010 the Developmetal Testbed Center (DTC) established the DTC Ensemble Testbed (DET) to facilitate the transition of academic research into operations. This seminar will give an overview of the various aspects of ensemble forecasting, including scientific and user requirements, the need to properly represent all sources of forecast uncertainty in the generation of ensembles, statistical post-processing of forecast output to enhance utility, the generation of various products from an ensemble, and the verification and evaluation of ensembles both from developers and users perspectives. Plans and progress on establishing the DET infrastructure in these areas will also be discussed.