In order for HIV treatment to be effective for a long time, it has been found that you need to take more than one medicines at a time. This is what is known as combination therapy or Highly Active Antiretroviral Therapy (HAART). The general recommendation is to use a minimum of 3 different drugs/medicines.

• Nucleoside Reverse Transcriptase Inhibitors (NRTI)
  The first group of ARV is the Nucleoside Reverse Transcriptase Inhibitors (NRTI). HIV needs an enzyme called reverse transcriptase in order to be able to infect healthy T-cells and reproduce itself. As the name conveys, NRTI inhibits reverse transcriptase that slows down the production of the reverse transcriptase enzyme and disable HIV infection and replication.
• Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTI)
  The second group of ARV is the non-nucleoside reverse transcriptase inhibitors (NNRTI). This group of drugs also stops HIV from infecting T-cells by intervening with the transcriptase of the virus. The NNRTI binds to the T-cell's reverse transcriptase, hence confusing the HIV virus. NNRTI drugs blocks the duplication and the spread of HIV.
• Protease Inhibitors
  The third type of ARV is the Protease Inhibitors (PI) group. As the name says, PI inhibits protease. Almost all living cells contain protease. Protease is a digestive enzyme that breaks down protein and is one of the many enzyme that HIV uses to reproduce itself. HIV attacks the long and healthy chains of enzyme & proteins in the cells and cuts them into smaller pieces.
  
  PI takes effect before HIV has a chance to attack the healthy enzyme and proteins. The NRTI and NNRTI only have effect on newly infected cells. PI can slow the process of immature HIV preventing HIV to mature, thus making them infectious. PI also work in cells that have been infected for a long time, by slowing down the reproduction of the virus.