Extremely low compared to the total growth: Per https://lemmy.fediverse.observer/dailystats Lemmy grew from 150,000 to 1,150,000 total users in the last four days, but for the active users, the growth was 30,000 to 39,000. If you extrapolate that, there are maybe 200,000 real Lemmy users now.
You click a link to some fediverse content somewhere, and actually land on the instance where you have a login and can interact with it.