Lentivirus is a type of retrovirus known for its ability to integrate into the host genome and persist for long periods, leading to chronic infections. It is characterized by a slow replication cycle and can infect both dividing and non-dividing cells. Lentiviruses are best known for causing diseases such as HIV (Human Immunodeficiency Virus), which can lead to AIDS. They are also used in research and gene therapy due to their capacity to deliver genetic material into various cell types.