  Semantic Web is actually an extension of the current one in that it
represents information more meaningfully for humans and computers alike. It
enables the description of contents and services in machine-readable form, and
enables annotating, discovering, publishing, advertising and composing services
to be automated. It was developed based on Ontology, which is considered as the
backbone of the Semantic Web. In other words, the current Web is transformed
from being machine-readable to machine-understandable. In fact, Ontology is a
key technique with which to annotate semantics and provide a common,
comprehensible foundation for resources on the Semantic Web. Moreover, Ontology
can provide a common vocabulary, a grammar for publishing data, and can supply
a semantic description of data which can be used to preserve the Ontologies and
keep them ready for inference. This paper provides basic concepts of web
services and the Semantic Web, defines the structure and the main applications
of ontology, and provides many relevant terms are explained in order to provide
a basic understanding of ontologies.
