I need to use the restroom.- need-an extreme want We are required by law to wear a seatbelt while driving a car.- required-forced

"Need" comes from old English and it meant "violence" or "force" when it was first used. "Require" comes from Latin and it meant "seek", "ask repeatedly for". Today the meanings of both words are very close. He is injured and needs medical attention. He is injured and requires medical attention. We all need food and shelter. A visa is not required to visit South Korea but I need to show my passport. "Require" expresses necessity and "need" expresses urgent want. I need a better Internet connection. A password is required to log-in. Good question!

The above is a good answer but one constant difference I find between need and require is where the necessity stems from. From the object with the need or the object that imposes the need. For example: I need a car for work. The job requires that I have a car. I need to eat. Survival requires that I eat. I need a pass to get in. Admission requires a pass. If anything imposes a need, I think it is safe to use require. Whereas if something has a need imposed, then it is usually safe to use need. Obviously, the word need has a little more versatility than the word require since a requirement is almost strictly an imposed need but a need could be either imposed or not.