Alts are a fun idea.
On Twitter and Discord people sometimes have multiple accounts. Often there's two: One is their "real face" and another is that other one. The "real face" gets used for "mundane" things—if people can see who I follow or what I say or what spaces I'm in on that account, it's not a problem. That's the "okay stuff." Then there's that other one, the "alt," that's secret. Often people say things there that they don't want associated with their "real face." They're not happy to admit those things.
This is funny—it's almost a literal translation of self and shadow.