They are applications that are run in the console, or the Command Line.
They have no actual GUI, though many use Ncurses to make "pretty" buttons instead of regular black and white text. Most are just text though.
Like when you run ./configure , make, make install, to install software, you are actually using GCC, a console app.
Many others include Links, a Text browser, mpg321 a console mp3 plater, cdrtools - console cd recording tools. There are thousands of others.
The CLI is what was before XFree86, so all apps were made in that at some point.