According to USA Today, as well as “stan” being used as a noun to describe a big fan of a celebrity, it can be used when somebody does something nice or something you consider cool, and you want to show your approval. For that reason, while you might hear someone describe themselves as a “Billie Eilish stan,” you’re just as likely to hear somebody say something along the lines of “Did you see his T-shirt? We have to stan!”
To add another dimension, you may also have heard of “Stan Twitter.” This is the name given to a broad Twitter community of people who discuss and are fans of celebrities and popular culture, with their own slang and inside jokes. While the main theory is that “stan” comes from the Eminem hit “Stan,” as it turns out, it might be merely a portmanteau of “stalker” and “fan,” per Bustle. Whichever explanation do you prefer, it’s clear that the word “stan” has evolved to have a much more light-hearted feeling.