A retrovirus is a RNA virus which can be duplicated in a host cell using the reverse transcriptase enzyme. It can produce DNA from its RNA genome. The produced DNA is then incorporated into the host's genome by anintegrase enzyme. The RNA virus thereafter replicates as part of the host cell's DNA. Retroviruses are enveloped viruses that belong to the viral family Retroviridae.
Provirus is a virus genome which can integrate into DNA of host cell. In inactive viral infections the virus will not replicate itself but through replication of its host cell. This state can last over many host cell generations.