MOTD - message of the day, it's the small text blurb that's printed when you start a new shell instance on linux or mac computers. Not sure if it's a thing on windows.
Which (readline, that is) is used in tons of command line programs, shells, REPLs, etc. to parse user input. So if you know the shortcuts you can apply them in tons of programs...
Readline refers to the GNU readline library [1]
1 - https://en.wikipedia.org/wiki/GNU_Readline