Species contains a group of individuals with the same morphological characters and they can breed among themselves. In the system of taxonomic classification, it is considered the last group of classification, containing organisms with more similarity than the other groups.
A taxon is simply a group of one or more population of an organism in taxonomical form. It is just a level of biological classification. eg: Family, order, class etc.
Species is a taxonomic category and can be said as a taxon.