4chan.org is a major website and imageboard most popular for its Japanese culture focus, as well as its '/b/ - Random' board. /b/ makes up the majority of the forum's traffic and is generally assumed to be representative of 4chan as a whole, especially to Facepunchers.
Though some FP'ers are users of 4chan, FP as a whole sees 4chan negatively. A mutual distaste of Reddit often brings many FP'ers to side with 4chan, though generally this would not happen except in times of notable conflict between the communities.
4chan is generally seen as full of pedophiles and "the bottom of the internet". /b/ is often likened to the OIFY. Many memes from 4chan become popular, sometimes only briefly, on FP, especially in LMAO Pics.