Inspired by this Meta post:
Just as travelers' immune systems can be assaulted by new diseases in new places, new users are increasingly likely to be miffed by an ingrained meme and left sitting scratching their heads.
It seems natural1 to collectively create a compendium of the concepts and ideas one may encounter through the site's posts, comments or chat.
These ideas not only reflect the good-hearted spirit of the community but also may summarize or abbreviate common knowledge gathered with time and that may help the reader to effectively and efficiently navigate the workplace.
Please include only one per answer, and explain it in a way understandable to those unfamiliar with it.
I hope that we all can contribute with our examples, as well as enhance, exemplify, and support the ones already shared. Please refrain from Memifying users without their approval; that's not cool.
Also remember that these posts are not the absolute truth, and should be taken more lightly than an actual answer on the main site. Remember to be respectful and to analyze these posts with your own judgment before considering its use.