text file vs webpage

text file and webpage both are nouns.

Word	Noun	Adjective	Verb	Adverb
text file	Yes	No	No	No
webpage	Yes	No	No	No

As nouns, webpage is a hyponym of text file; that is, webpage is a word with a more specific, narrower meaning than text file:

text file: (computer science) a computer file that contains text (and possibly formatting instructions) using seven-bit ASCII characters
webpage: a document connected to the World Wide Web and viewable by anyone connected to the internet who has a web browser

Other hyponyms of text file include web page, ASCII text file.

text file (noun)	webpage (noun)
(computer science) a computer file that contains text (and possibly formatting instructions) using seven-bit ASCII characters	a document connected to the World Wide Web and viewable by anyone connected to the internet who has a web browser