A Temporal.TimeZone is a representation of a time zone: either an IANA time zone, including information about the time zone such as the offset between the local time and UTC at a particular time, and daylight saving time (DST) changes; or simply a particular UTC offset with no DST.
Since Temporal.Absolute and Temporal.DateTime do not contain any time zone information, a Temporal.TimeZone object is required to convert between the two.
Finally, the Temporal.TimeZone object itself provides access to a list of the time zones in the IANA time zone database.
An API for creating custom time zones is under discussion. See Custom Time Zone Draft for more information.