Viruses are not cellular. Although they reproduce, they can only do so only by entering a host cell and making use of its machinery for replication.
Viruses are bits of genetic material, apparently derived from their hosts.
Tailed phages Myoviridae. Phages with contractile tails. Phages with short tails. Phages with long non-contractile tails. Tectiviridae dsRNA viruses Birnaviridae.