How do over-the-counter medications differ from prescription medications?

Over-the-counter (OTC) medications are designed to be safe and effective for use without the direct supervision of a healthcare provider, which is why they can be purchased without a prescription. This accessibility allows consumers to manage common ailments such as headaches, colds, and allergies on their own, making them readily available in pharmacies and retail stores.

In contrast, prescription medications typically require a doctor's approval to ensure they are appropriate for a patient's specific condition and to monitor potential side effects or interactions with other medications. This necessity for professional oversight is a key distinction between the two types of medications, emphasizing the importance of medical guidance in certain cases. Therefore, the defining characteristic of OTC medications is indeed that they can be bought without a prescription, which aligns with the correct answer.