From WikiPedia:

The Jervis Bay Territory (/ˈdʒɜːrvɪs, ˈdʒɑːr-/; “JBT”) is an internal territory of Australia. It was established in 1915 by the transfer of jurisdiction from the state of New South Wales to the federal Commonwealth of Australia, in order to give the federal government control of a port in the vicinity of the landlocked Australian Capital Territory (ACT).

I am 45 and did now know this until today when for some reason Jervis Bay Territory was printed in a select option along with the other Australian states and territories.