User identities, or user identifiers, are specific attributes that can be used to identify known users. Examples of user identities include:
- Phone number
- Customer ID
- Email address
User attributes can be any set of free-form key/value pairs describing a user. For example, a name, frequent purchase, or date last seen. There is a list of reserved user attributes, which can be found in Reserved Attributes.
For more information about user attributes, refer to User Attributes for examples specific to the web SDK.
Specific examples for other platform SDKs can be found in the appropriate Client SDKs section of our Developer docs.