The life cycle is divided into many phases
The first phase is the attachment of the virus to an immune cell, which is the first process of infection and ends with the new virus budding out of the infected cell. Just as the influenza virus has an affinity for the cells of the respiratory tract (lungs), so HIV has an affinity for the immune system cells—especially the T helper cells (known as a CD4 T Cell).
When the protruding portions of HIV come in contact with the CD4+ cellular receptor of the cell, various changes occur which allow the virus to fuse to the host cell (fusion), and the genetic material of the virus is able to enter the cell.
Once the virus has entered the cell, the viral RNA (originally in its own capsid) is released into the cell - followed closely by the production of double-stranded DNA from single-stranded RNA (third phase). The reverse transcriptase enzyme assists in this process.
The viral DNA is then integrated into the host DNA using another viral enzyme called retroviral integrase. Simply put, the viral DNA has now hijacked the host DNA and is able to produce more virus RNA through a process called transcription. RNA is produced in several forms as part of the process that will help produce viral proteins, and eventually form new viral particles. The protein building blocks are cleaved (joined) using another viral enzyme called protease, and migrate to the edge of the cell as viral proteins to form new viruses (virions).
The final phase is called budding. As the new virus moves out of the cell it takes with it part of the cell outer membrane as part of its own structure. Once outside the cell the virions mature to form new infectious viruses that may go on to infect more cells and repeat this process.