Modern drug marketing has me confused about even the most simple over the counter choice.
Aspirin, also known as acetylsalicylic acid, is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. wikipedia 
Acetaminophen, also known as Paracetamol, is a widely used over-the-counter analgesic (pain reliever) and antipyretic (fever reducer). Common trade names: Tylenol and Panadol. wikipedia
Ibuprofen, is a nonsteroidal anti-inflammatory drug derivative of propionic acid used for relieving pain, helping with fever and reducing inflammation. It was originally marketed as Brufen. Common trade names: Advil, Motrin and Nurofen. wikipedia
Naproxen, usually sold as the sodium salt naproxen sodium, is a nonsteroidal anti-inflammatory drug in the same class as ibuprofen and is commonly used for relief of a wide variety of pain, fever, swelling and stiffness. Common trade names: Aleve, Naprosyn. wikipedia