Unlike the States of the Union or a Commonwealth (Union of several sovereign states), the US territories are considered as sub-national administrative divisions, this means that these territories are without sovereignty and thus they lack representation in Congress and are administered directly by the federal government.
These territories can be classified as incorporated or unincorporated as well as if they have an organized government or not.
It's important to make a note here since the US has 16 territories, 5 of which are inhabited and have a government (Guam, American Samoa, US Virgin Islands, Northern Mariana Islands, and Puerto Rico) and 11 which are islands with no population or government.