The main difficulty associated with the B2C domain is increasing the usefulness of WWW for the electronic trade through the improvement of the services provided to the consumer. Even though the WWW allows the buyer to have access to a great amount of information, to obtain the information from the right supplier that sells the desired product by a reasonable price can be a very expensive task. One of the ways of improving the web functionality is through the use of intelligent agents for search of information, that is, the introduction of purchase agents that aid the buyers to find products of their interest. For that to happen we need to overcome an inherent difficulty of the WWW: the mixture of natural language, images and layout information in HTML is one of the greatest barriers for the automation of the electronic trade, because the semantics of the information is only comprehensible for human beings. To solve this problem we hope to produce more efficient purchase agents by associating them to the use of ontologies, and virtual stores that have special annotations that follow ontologies. In the present dissertation we make a study of the main technologies related to ontologies development in computer science. We also develop a case study about the ontologies application to the B2C domain, seeking in this way to evaluate potential and existing difficulties for the development of this type of application.