A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
Separate names with a comma.
EASY SOLUTION//: I have found an EASY SOLUTION for the 'SIGN IN' and 'CREATE ACCOUNT' buttons not working in Unity hub versions 3.0.0 and above....
This only lets you download an older version of unity and not the unity hub.