Viruses have evolved a remarkable diversity of strategies for spreading efficiently from one host to the next. Organisms feeding on infected hosts and actively traveling in between hosts in the environment are all potential useful means for virus transport. Such organisms, designated vectors, are found among fungi, nematodes, and arthropods, particularly insects. Several different interaction patterns have evolved between viruses and vectors, and this diversity is well illustrated in plant viruses transmitted by insects. Over half a century, a tremendous amount of studies has been carried out on the insect transmission of viruses, and a classification of the strategies observed has been established and regularly updated. This classification, originally established for the insect transmission of plant viruses, is comprehensive enough to illustrate all strategies described so far for virus–vector interactions, including animal viruses (though not addressed in detail here) and the cases of transmission by non-insect vectors such as mites, nematodes, and fungi. This article presents an overview of this classification, illustrated by appropriate examples.