The hallmark of HIV-1 is its extensive genetic diversity that emanates mainly from high mutations. Phylogenetically, HIV can be classified into geographically confined groups, types, subtypes and circulating recombinant forms (CRFs) that are however subject to change over time. HIV genetic diversity may partially explain the observed heterogeneity in HIV prevalence and has also been reported to impact on viral transmissibility and differential rates of disease progression. The aim of this review is to present a simple overview of the principles and concepts of HIV diversity and classification. Tracking the presence of new HIV strains is not only important for surveillance purposes but is also critical in facilitating personalized targeted therapy as well as forming the basis for development of the much anticipated effective vaccines against this scourge.