The Human Immunodeficiency Virus type-1 (HIV) belongs to the Family Retroviridae.

In HIV, RNA is the template for the synthesis of DNA. This differs from most cellular biochemistry in which DNA is used as the template for the synthesis of RNA.

The enzyme that transcribes the RNA for the synthesis of DNA is called reverse transcriptase.

Because of the enzyme's activity, HIV is known as a retrovirus - retro implying reverse.