Darth Rosenberg said:
Y'know, I still don't quite understand what all this use of / and individual letters means... I can't help but think of the Blur lyric, 'texting, abbreviates the brain' (from Brothers And Sisters), that it's all reducing and abbreviating (expression and thought) into a singularity of absolute idiocy and echo chambers, and it's not helping anyone or anything. The thing designed to facilitate communication is actually sabotaging communication.
In case you are legitimately confused rather than venting, its shorthand for a web address.
When you go to a thread on the escapist, and see its in the "Gaming discussions" section, it has a /forums/read/[Set of random numbers here]-[Title here]-[Page # here] appended on to the end of www.escapistmagazine.com
When on, for example, the gaming subsection of reddit, you are at www.reddit.com/r/gaming. Hence, the gaming subzone is referred to as r/gaming, because its a simple shorthand of the URL that references exactly where you found certain threads.
Likewise, users are www.reddit.com/u/[Username], and can be tagged in a Reddit post by typing u/[Username], sending a PM to the person to check that post. Hence users on reddit are often referred to as u/[Username], as it clarified you're talking about a user rather than a subzone [Some users have unintuitive names], and allows you to tag them if on Reddit so they can join in on whatever you're talking about them for. And, again, its shortening the URL.
From what I understand, its similar on 4chan, just their naming conventions are often... Weird. For example, our "Wild West" forum is the equivalent of /b/ on 4Chan IIRC, and thus that part of 4chan is referred to as /b/, to reference the different segmented communities on the site. Thus, if you wanted to refer to any posts from that specific community, which is just named /b/, you can't say anything but /b/ to label them. Its a weird naming convention, and some like /mlp/ and /pol/ make some more sense, but hey.
So, by and large its not actually an abbreviation done to shorten things, its a direct reference to where something is found. Either a subreddit via r/[Subreddit name], or a board on 4chan with /[boardname]/. Subreddits tend to be intuitively named, usually, but there's so many of them [I.E: r/games, r/gaming, r/oldschoolgaming, r/gamedev, r/truegaming, r/gametales, r/indiegaming, r/gamedeals and literally a hundred more] that saying "The gaming subreddit" is actually a rather broad statement, so defining it specifically at the subreddit at address r/gaming is a much better way of communicating it.