What is rule 34.xxx?

Rule 34 is an internet adage that asserts: "If it exists, there is porn of it." This concept is a part of internet culture and is often referenced to highlight the vast, unexpected, and sometimes bizarre range of adult content that can be found online. The "xxx" suffix you mentioned is likely a nod to adult content, as "xxx" is commonly used to denote explicit material.

Rule 34 is not an actual regulation or formal rule but rather a humorous observation about the nature of internet content driven by user-generated material. Keep in mind that this saying is meant to be taken lightheartedly and is often used in discussions related to online communities and the nature of content on the internet.