Sinus refers to air-filled cavities located within the bones around the nose and eyes. These cavities play a crucial role in producing mucus, which helps moisten the nasal passages and trap dust, pollutants, and microorganisms. Healthy sinuses are vital for comfortable breathing and preventing infections. However, when sinuses become inflamed or blocked due to allergies, infections, or structural issues, it leads to sinusitis. Symptoms include nasal congestion, facial pain, headaches, and pressure. Effective management involves proper hydration, steam inhalation, nasal irrigation, or medications like decongestants and antihistamines. In chronic cases, medical intervention, such as surgery, may be required for lasting relief.