In taxonomy, organisms are classified into various hierarchical ranks. Examples of taxonomic ranks are species, genus, family, order, class, phylum, kingdom, domain, etc.
Species:The lowest taxonomic rank, and the most basic unit or category of biological classification.
Genus: Any of the taxonomic groups into which a family is divided and which contains one or more species. In the hierarchy of biological classification, genus comes above species and below family.
e.g. Mangifera indica is the scientific name of mango where Mangifera is the genus name and indica is the species name.