In order for HIV to successfully take over a CD4 cell's machinery so that it can produce new viruses, HIV's RNA is converted into DNA by the reverse transcriptase enzyme (nucleotide/nucleoside reverse transcriptase inhibitors can block this process). After the "reverse transcription" of RNA into DNA is complete, HIV's DNA must then be incorporated into the CD4 cell's DNA. This is known as integration. As their name implies, integrase inhibitors work by blocking this process.
Integrase inhibitors may offer a lot of hope for HIV-positive people, especially those who have developed HIV resistance to drugs that target HIV's two other major enzymes: reverse transcriptase and protease.