Gene Ontology, or GO, is a collaborative effort to address the need for consistent descriptions of gene products in different databases, their placement in cellular components, and their molecular functions in a species-independent manner. Terms in each of the vocabularies are related to one another within a vocabulary in a polyhierarchical (or directed acyclic graph) manner.
Tools for Browsing GO - Gene Ontologies and Bioinformatic Tools and Software for Viewing GO
New terms and annotations are suggested by members of the research community. Once submitted, they are reviewed by members of the GO consortium to determine their applicability.
Also see the Gene Ontology Consortium — GO Consortium provides access to ontologies, software tools, annotated gene product lists, and reference documents describing GO and its uses.