A Listpoint User is someone who has registered for an Account and been approved. Application instances may also be registered as Users so they can receive alerts when Contexts or Context Maps change and thus download and install new versions.
A User can also have one or more User Roles. A User Role enables you to edit items.
Being a member of the right Teams and having the right User Roles allows you to edit and publish items.
Being a registered User of JoinedUpSystems.net gives you access to just the Code List Management Service (CLMS) at present.
How To guides for Users are here