Virus classification is the process of naming viruses and placing them into a taxonomic system. Species names generally take the form of [Disease] virus. Similar to the classification systems used for cellular organisms, virus classification is the subject of taxonomists. The International Committee on Taxonomy of Viruses (ICTV) is the only body charged by the International Union of Microbiological Societies with the task of developing, refining, and maintaining a universal virus taxonomy - see ICTV classification.
Baltimore classification (se picture) is a classification system that places viruses into one of seven groups depending on a combination of their nucleic acid (DNA or RNA). In the original @ Virus Classification - Wiki Article also subviral agents like viroids, satellits and prions are described. They are smaller than viruses but have some of their properties.