A important use of your NetID is for authentication that allows access to Duke resources - computing or otherwise. Authentication establishes your identity as a particular user. Once that identity is established, your authorization to use particular services at specific levels of privilege follows.
Authentication modes vary.
Some services present a custom login screen or dialog that prompts for a userid and password. This is single-factor authentication.
Other services will present a Duke login screen that requires your NetID credentials and a secondary form of authentication from some other device (phone, tablet, or token). This is multi-factor authentication.
Over time more services have moved from single-factor to multi-factor authentication. Expect that trend to continue.
In short, your NetID credentials establish your identity at Duke and are essential now for most tasks. Contact the OIT Help Desk (684-2200) or visit the LINK service desk with any questions.