A defect is a problem with the quality of something. It is often used in regards to the manufacturing quality of a product. For example, "I bought a new cell phone, but it has a defect, so it doesn't work correctly. It is defective." A drawback is a reason why something is not so good. A drawback = a disadvantage. For example, "I love to run, but a drawback is that it hurts my knees sometimes."

Thank you Alex and Seth.I got it

A "drawback" is like a trade off, its is minor neggative effect that you get from something like a action. A "defect" is usually used to describe a items that has something wroung with it. For example " this car has a defect where the headlights don't come on"