Reverse transcriptase is an enzyme whose function is to create single stranded DNA (cDNA) from RNA template (hence it's name "reverse"). This enzyme is found primarily in retroviruses. One significant example of such retrovirus is HIV. This virus contains the reverse transcriptase that allows it to produce complementary DNA and start creating it's own proteins and multiply, generating new viruses. Drugs, known as reverse transcriptase inhibitors, inhibit the function of reverse transcriptase and therefore suppress the growth of the virus.