What's the difference between these three? In particular between the second and third one:
Representative for a state
Delegate for a territory
Resident Comissioner of a territory
According to the article in Wikipedia, the last two titles have the same function in the United States. Wikipedia appears to say that the usage of the two terms is for historical reasons, but that they are currently identical in function.
Wikipedia states at Resident Commissioner
The Resident Commissioner of Puerto Rico does not reside there but represents the U.S. commonwealth in the continental United States, particularly in the capital of Washington, DC. He represents Puerto Rico in the United States House of Representatives, where the Resident Commissioner has a status equivalent to a territorial delegate, as well as before executive departments.
The Resident Commissioner of the Philippines held a similar position when the Philippines was a United States territory and then Commonwealth. The position was originally created by the Philippine Organic Act of 1902 with the first commissioners serving from 1905. The position ended with Philippine Independence in 1946.
In most other U.S. overseas (and historically pre-state) territories, a similar representative position is styled Delegate.
Non-voting members of the United States House of Representatives include non-voting delegates and resident commissioners.
They are non-voting members who are elected from a U.S. territory or from Washington, D.C., to a two-year term (with the exception of the one representing Puerto Rico, who is elected to a four-year term). While unable to vote in the full House, a non-voting member may vote in a House committee of which the delegate is a member, as well as introduce legislation. There are currently six non-voting members, representing Washington, D.C., Puerto Rico, American Samoa, Guam, the Northern Mariana Islands, and the U.S. Virgin Islands.