"HIV stands for human immunodeficiency virus. It weakens a person’s immune system by destroying important cells that fight disease and infection. There is currently no effective cure for HIV. But with proper medical care, HIV can be controlled. Some groups of people in the United States are more likely to get HIV than others because of many factors, including their sex partners and risk behaviors" (CDC "HIV Basics").
"PrEP (pre-exposure prophylaxis) is medicine people at risk for HIV take to prevent getting HIV from sex or injection drug use. When taken as prescribed, PrEP is highly effective for preventing HIV" (CDC "PrEP").
"PEP (post-exposure prophylaxis) means taking medicine to prevent HIV after a possible exposure. PEP should be used only in emergency situations and must be started within 72 hours after a recent possible exposure to HIV" (CDC "PEP").