As Wikipedia explains, articles on fiction can approach their subject from two angles.
In one method, articles can describe the subject matter from the perspective of the real world. This may include real-world factors that have influenced the work and a critical analysis of the subject. This is often called an out-of-universe perspective.
The second approach treats the fiction as if it were real, and describes it from the perspective of the people and characters of the fictional universe. Topics covered may include the birth and death dates of fictional characters, a plot synopsis framed as biography, and fictional background information. This is often referred to as an in-universe perspective.
To further distinguish the Buffy Wikia from Wikipedia, writing from an in-universe perspective, or a "Buffyverse perspective" is strongly encouraged here. Information on authors and actors are included for background information and these will be written from an out-of-universe perspective, but epiosodes can be written about as though they really happened.