Basically, an NDA is a way to keep your “secret” information secret—whether you’re dealing with friends or not.
You will want an NDA when you are presenting, sharing, showing, receiving, or allowing outsiders to access your confidential information.

In other words, Non-Disclosure Agreements (NDAs) are legal agreements that protect sensitive information that contribute to projects, ideas, or products of the company and keep that information out of the hands of competitors.