RTFM frequents questions that common sense should have precluded asking.
Some may choose to reply in this fashion rather than leaving the newbie without a response so as to clarify what types of questions are considered inappropriate, unintelligent or inconsiderate of others' time.
originally: "read the field manual" used by WWII soldiers when asked basic questions by new enlistees.
rtfm quickly spread to engineering, computer & technical fields, and has gained popularity with internet usage.
its applicability has increased dramatically with the advent of wiki, where the answer is already at everyone's fingertips.
rookie: how am i supposed to clean this m1?
veteran: read the field manual.
noob: how do i install linux?
1337: rtfm @ linux.org/docs/beginner/install.html
polite usage that will increase likelihood of a helpful response:
newbie: how do i...? i have already rtfm.