A provirus is a virus genome that is integrated into the DNA of a host cell. In the case of bacterial viruses (bacteriophages), proviruses are often referred to as prophages. However, it is important to note that proviruses are distinctly different from prophages and these terms should not be used interchangeably. Unlike prophages, proviruses do not excise themselves from the host genome when the host cell is stressed.[1][page needed]
This state can be a stage of virus replication, or a state that persists over longer periods of time as either inactive viral infections or an endogenous viral element. In inactive viral infections the virus will not replicate itself except through replication of its host cell. This state can last over many host cell generations.
Endogenous retroviruses are always in the state of a provirus. When a (nonendogenous) retrovirus invades a cell, the RNA of the retrovirus is reverse-transcribed into DNA by reverse transcriptase, then inserted into the host genome by an integrase.
A provirus not only refers to a retrovirus but is also used to describe other viruses that can integrate into the host chromosomes, another example being adeno-associated virus. Not only eukaryotic viruses integrate into the genomes of their hosts; many bacterial and archaeal viruses also employ this strategy of propagation. All families of bacterial viruses with circular (single-stranded or double-stranded) DNA genomes or replicating their genomes through a circular intermediate (e.g., tailed dsDNA viruses) have temperate members.[5]
https://en.wikipedia.org/wiki/Provirus
A prophage is a bacteriophage (often shortened to "phage") genome inserted and integrated into the circular bacterial DNA chromosome or exists as an extrachromosomal plasmid. This is a latent form of a phage, in which the viral genes are present in the bacterium without causing disruption of the bacterial cell. Pro means "before", so, prophage means the stage of a virus in the form of genome inserted into host DNA before being activated inside the host.
https://en.wikipedia.org/wiki/Prophage
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