What are specific relations between Web-semantic and ontology (Uschold, 2005)? What is an ontology of a domain? What are the relations between texts relative to a domain and an ontology of this domain? How to build an ontology from texts (Aussenac-Gilles et al., 2005)? In our approach of these questions, we consider that there are different levels of ontologies: (i) ontology of a domain; (ii) ontology of relations that leads to a semantic map for structuring the ontology of a domain; (iii) general ontology, or upper ontology, that gives formal semantic representations of concepts, definitions by combining semantic primitives and inference rules. The aim of this paper is to introduce, for further discussions, clear and formal distinctions between three levels of ontology: the ontology specific to a domain with first-level-concepts and classes of instances; second- level-concepts of a semantic map relative to a notion (as cause, action, localization of events in space or in time, meeting between different peoples...); third-level-concepts of a general ontology where are interpreted the second and first levels concepts by means of schemes (l-expressions with types) and different (functional) types of objects. We plane also to explain how these levels are articulated between them.