Seeing almost everyone posting cats, what's going on?

There are many things I'm yet to understand on this app; do people get to send private messages here? What mostly go on in this space? Cause the posts I mostly see are quite serious, no one really dropping comments under people's posts etc, unlike the other social media apps. Or is there something I'm not understanding yet? Lol
Ain't nobody got their pictures on here? Can't seem to find any 🤔🤔
Is there perhaps a place on this app I do not know about? 😭 please and please just signify one way or the other if you happen to see this post because this place getting boring day by day. Not fair 😭