药 (yào) is the everyday word for 'medicine' — what you take when you're sick. At HSK 5, 药物 (yào wù) and 药品 (yào pǐn) are more formal, written terms: 药物 refers to medication as a substance, while 药品 emphasizes pharmaceutical products (e.g., regulated drugs). 药 is also used in compounds like 毒药 (poison) or 炸药 (explosive), but at HSK 2 it simply means medicine.