/vt/ - Virtual Youtubers

When introducing a new character that (You) in the story already know, is it best to write a short explaination paragraph outlining who they are and how they're connected? Or do you reveal that over time through dialogue?
I feel like with the latter you could be leaving the reader in the dark for too long, but I guess the former could be seen as "telling not showing" and might seem like an exposition dump. I've seen actual authors do both, though the former option seems more common. What do you guys think?