To clarify a bit: 4chan is a site that's very split. The most popular 4chan community is the /b/ (random). Think of it as a forum and it makes it very easy to look around when you get used to it. Now /b/ is the place everyone heard about when it comes to 4chan. It's gore, nudity, trolling and everything else in there (with a certain "smile" on the lip). To defend, there's also other communities like anime, wallpaper etc. like reddit if you've been there, which is far less worse than 4chan's /b/ community.