/b/ is the "random" board. I don't particularly know why it's b, must be from its japanese days or something. Most of the others are from english though
4chan's forum has many different sections for posting pictures.. when you enter in one of them, there will appear a strange "alphabet" on the top of the screen
[a / b / c / d / e / f / g / gif / h / hr / k / m / o / p / r / s / t / u / v / w / wg] [i / ic] [cm / y] [r9k] [an / cgl / ck / co / fa / fit / hc / jp / mu / n / po / sp / tg / toy / trv / tv / x] [rs] [status]
This is used for changing between sections without having to go back to the main page (It's useful except that you'll have to guess which of these go to the section you want), and it follows the design of Futaba Channel's Nijiura board.
When you enter a section, for example b, the link on the address bar will look like that: http://img.4chan.org/b/imgboard.html
And so will it show on the page:
/b/ Random
Example of another section (since the random one is messed up so much)
If you want to know more, check 4Chan on Wikipedia, I learned everything I know of 4chan in there, it's very useful
Well if you were accessing 4chan when people on /b/ were all like "z0Mg 100M GET!!!!!!!", you'd know what I mean by messed up, and so I couldn't take a screenshot of the "/b/ Random" section for my post above since it was renamed to this
Read the article too, was zo funny when he started about his male car.
I can picture something of how you have sex with a "female" car, but I'm still wondering what he's doing with the male one..