Emtricitabine and tenofovir disoproxil fumarate (Truvada) for pre-exposure prophylaxis (PrEP) is a once-daily prescription medicine for adults and adolescents at risk of HIV who weigh at least 77 pounds.

Explanation

Truvada is a medicine people at risk for HIV should take to prevent infection with the virus from various ways, such as sex or injection drug use.
PrEP consists of a combination of 2 antiretroviral drugs (tenofovir and emtricitabine), usually taken daily and often in combination with other HIV medicines.
When taken consistently, the Centers for Disease Control and Prevention estimates that PrEP reduces the risk of HIV infection by up to 92%.

Reference