Selecting appropriate learning services for a learner from a large number of heterogeneous knowledge sources is a complex and challenging task. This article illustrates and discusses how Semantic Web technologies such as RDF [resource description framework] and ontology can be applied to e-learning systems to help the learner in selecting an appropriate learning course or retrieving relevant information. It presents the main features of an e-learning scenario and the ontology on which it is based, then illustrates the scenario ontology with the training domain and the application domain. Finally, it presents semantic querying and semantic mapping approaches.