The goal of Semantic Web is to build a web of meaning. This vision can be demonstrated if people and applications can create and discover new and interesting knowledge and share this knowledge in a transparent manner similar to the way data is exchanged today. Therefore, it is believed that Semantic Web will consist of a distributed environment of shared and interoperable ontologies, which have emerged as common formalisms for knowledge representation. Users will need to discover new knowledge that is not known to them before and use it to either annotate the content or to formulate their information requests. This requires an environment that supports creating, maintaining, and controlled sharing of ontologies. A Peer-to-Peer (P2P) infrastructure can enable such capabilities. This thesis proposes an approach called P2P Semantic Web (PSW) with capabilities of finding relevant sets of ontologies, facilitating reuse of existing ontologies to create additional ontologies, and advertising the resulting ontologies. It discusses an ontology driven search of concepts and exploration of interontological relationships over a P2P infrastructure. The prototyping of this approach in the InfoQuilt system is also discussed.