text file vs txt

text file

noun
  • A data file in a character encoding that allows it to be read in non-specialised text editor. 

  • A data file containing only plain, human-readable text, distinct from documents with embedded formatting 

txt

noun
  • text, text message 

verb
  • To text; to send a text message (to). 

How often have the words text file and txt occurred in a corpus of books? (source: Google Ngram Viewer )