This talk introduces concepts, approaches and systems architectures related to the integration and the 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 concern: -The basics of interoperability: problem statement, approaches and architectures for interoprability -Ontology and Semantic Annotations -Location and Roles of Semantics in the Interoperability Process -Enterprise Modeling and Large Scale Semantic Interoperability -Supporting Environments for Semantic Interoperability