Every user has a profile. User profiles store information about a user. They are created when a user registers with your site or logs in using an external provider, and can be updated by a user from their My Account page.
Profiles must have an email address and a name. Everything else is optional.
How Profiles Work
User profiles are managed by forms. A form defines all of the fields, like name, address, phone number, a user can enter. Forms are also used to update a profile.
See the User Profiles page for a more technical look at how the forms work.
You can store almost anything against a user's profile. The data you store can also be shown or hidden, depending on the user. Because profiles are viewed and managed by forms, you have complete control over what a particular user can see.
We've seen profiles that store internal IDs needed when accessing other systems, as well as staff views of profiles that include warning flags about the user, both of which are completely invisible to the user concerned.