This talk introduces concepts and approaches related to the integration and interoperability of enterprise systems and software i.e. their ability to exchange "things" (data, models, and so on) together with their ability to cooperate in tasks achievement. The talk also introduces issues related to the use of ontologies and semantic annotations for semantic interoperability purposes. The main topics that are addressed concerns: - The basics of interoperability: problem statement and approaches - Ontology and Semantic Annotations - Location and Roles of Semantics in the Interoperability Process - Entreprise Modelling and Large Scale Semantic Interoperability - Supporting Environments for Semantic Interoperability