It's user accounts, not users of course. For instance, some people have alts, even a lot of alts in some cases! There are about 500,000 user accounts active every day according to this stats site, that's a better measure of activity, but total accounts milestones are fun 😁🎉 bsky.jazco.dev/stats

Yes and no. Many users are active users (i.e. they actively read posts) yet do not create posts or even like posts.