Semantic technologies are a new wave of computing, using explicit representation of meaning to enable data interoperability and more powerful and flexible information services and transactions. At the core of semantic technologies are ontologies, which capture meaning explicitly and may be used to manipulate and reason over information via its semantics. Unlike traditional data schemas or models, ontologies are capable of representing far more complex relations, may be linked directly to the data they describe, and have a formal logical semantics, facilitating automated deductive reasoning. This chapter introduces the vision of semantic technologies, and provides an overview of the approach and the techniques developed to date. It provides both an executive summary and an orienting framework for reading more technical material.