Coronavirus (COVID-19) is one of the most significant global health challenges in recent history. It is a viral disease caused by a strain of coronaviruses known as SARS-CoV-2. The virus first emerged in late 2019 and rapidly spread worldwide, affecting millions of people. The primary mode of transmission is through the respiratory system. The virus spreads via respiratory droplets released when an infected person coughs, sneezes, or even talks. It can also be transmitted by touching contaminated surfaces and then touching the mouth, nose, or eyes. The risk of infection increases significantly in crowded and poorly ventilated spaces. Therefore, good ventilation and physical distancing are essential preventive measures. Once the virus enters the human body, it mainly targets cells of the respiratory tract. It binds to specific receptors on the surface of cells, especially the ACE2 receptor. These receptors are abundant in lung cells, making them a primary target. After binding, the virus enters the cell and begins to replicate. This replication damages the cells and triggers an immune response. Common symptoms include fever, dry cough, and shortness of breath. In severe cases, the disease may progress to pneumonia. This can lead to acute respiratory distress syndrome (ARDS). In this condition, the alveoli fill with fluid, impairing gas exchange. As a result, the patient may suffer from severe oxygen deficiency. This can also lead to failure of other organs due to lack of oxygen. The severity of the disease varies from person to person. Some individuals experience mild symptoms or remain asymptomatic. Others, especially the elderly or those with chronic illnesses, may develop serious complications. The immune system plays a crucial role in determining disease severity. In some cases, a “cytokine storm” occurs. This is an excessive immune response that causes additional tissue damage. To prevent infection, several simple and effective measures are recommended. These include regular handwashing and wearing masks in crowded places. Vaccination is one of the most effective ways to reduce the spread and severity of the disease. Vaccines have significantly lowered the number of severe cases and deaths. In conclusion, COVID-19 highlights the importance of public health awareness and collective responsibility. Addressing such pandemics requires scientific understanding and responsible behavior from everyone.