tanker vs cargo vessel

tanker and cargo vessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
tanker	Yes	No	No	No
cargo vessel	Yes	No	No	No

As nouns, cargo vessel is a hypernym of tanker; that is, cargo vessel is a word with a broader meaning than tanker:

Other hypernyms of tanker include cargo ship.

tanker (noun)	cargo vessel (noun)
a cargo ship designed to carry crude oil in bulk	a ship designed to carry cargo
a motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads.
a soldier who drives a tank