Hello,
Auth0 handles the authentication and returns a token, Users with valid tokens can gain access to data from the Strapi back end that requires authentication. The user data can be fetched from Auth0. Authenticated data fetched from Strapi requires that the token be passed along for a user to be granted access. This method will be best for front end applications already implementing authentication using Auth0. I personally would not recommend this if the application does not already implement authentication using Auth0 before integrating with Strapi. Regardless, this is just my opinion and I stand to be corrected. Hope this was helpful, thanks.