A phage is a virus that behaves as a parasite on bacteria and is also referred to as bacteriophage. A temperate phage, is a phage that is able to exist as a prophage while it lives within its host at any point of its life cycle.
Such a phage is known as a lysogen, and it is said to display lysogeny. The phages can integrate their complete genetic information (genome) into that of the bacteria that host them, and a temperate phage can infect the host bacteria. On infecting the bacteria, it can either behave like virulent phage by entering into the lytic cycle or can get into a symbiotic relationship with the hosting bacteria. When behaving in the latter way, the phage is carried on to the descendants of the hosting bacteria.