This is the life cycle of HIV.

HIV is an RNA virus. Reverse transcriptase can use HIV RNA as template and deoxynucleotide as raw material (or substrate) to synthesize double-stranded DNA and integrate it into the host genome.

Nucleoside reverse transcriptase inhibitor (NRTIs) is an analog of deoxynucleotide, which is a reverse transcriptase substrate for HIV to synthesize DNA and is transformed into an active nucleoside triphosphate derivative in vivo. It is difficult for reverse transcriptase to distinguish which substrate is really useful, so inhibitors will compete with natural deoxynucleoside triphosphate. The substance produced by the combination of inhibitors and HIV reverse transcriptase (RT) has no DNA biological activity, which can further hinder the synthesis of provirus.