Antiretroviral drugs are medications that are used to treat HIV (Human Immunodeficiency Virus) infection. There are several different classes of antiretrovirals that work in different ways to inhibit the virus and slow the progression of the disease. The main classes of antiretrovirals include:

1. Nucleoside reverse transcriptase inhibitors (NRTIs): These drugs work by inhibiting the enzyme reverse transcriptase, which is responsible for converting HIV's genetic material (RNA) into DNA. This prevents the virus from replicating and spreading within the body.
2. Non-nucleoside reverse transcriptase inhibitors (NNRTIs): These drugs work in a similar way to NRTIs, but they bind to a different part of the reverse transcriptase enzyme.
3. Protease inhibitors (PIs): These drugs work by inhibiting the enzyme protease, which is responsible for processing the proteins that are needed for HIV to replicate. By blocking protease, PIs prevent the virus from producing new copies of itself.
4. Integrase inhibitors: These drugs work by inhibiting the enzyme integrase, which is responsible for inserting HIV's genetic material into the DNA of host cells. By blocking integrase, these drugs prevent the virus from establishing itself in the body.
5. Fusion inhibitors: These drugs work by blocking the virus from entering host cells.

Antiretroviral therapy (ART) typically involves the use of a combination of drugs from different classes in order to maximally suppress the virus and prevent resistance.