end user vs user

end user and user both are nouns.

Word	Noun	Adjective	Verb	Adverb
end user	Yes	No	No	No
user	Yes	No	No	No

As nouns, user is a hypernym of end user; that is, user is a word with a broader meaning than end user:

end user: the ultimate user for which something is intended
user: a person who makes use of a thing; someone who uses or employs something

end user (noun)	user (noun)
the ultimate user for which something is intended	a person who makes use of a thing; someone who uses or employs something
	a person who uses something or someone selfishly or unethically
	a person who takes drugs