OAuth 2.0 vs Auth0

Solution 1:

OAuth 2.0 is a standardized authorization protocol, Auth0 is a company that sells an identity management platform with authentication and authorization services that implements the OAuth2 protocol (among others).

Solution 2:

OAuth 2.0 is a protocol that allows a user to grant limited access to their resources on one site, to another site, without having to expose their credentials.

Auth0 is an organisation, who manages Universal Identity Platform for web, mobile and IoT can handle any of them — B2C, B2B, B2E, or a combination.

Source

Solution 3:

In case if you cannot understand any of above,

• OAuth 2 - is a standard or protocol to implement authorization for any kind of software (windows, mobile or web)
• Auth0 - is a software product (cloud and on-prim), that implement top of OAuth2 and other standards. You can use Ath0 to simplify your authentication and authorization requirement.