Smartphone icons have green dot facebook and play store - why?

When the text message and Messenger icons have a green dot, it means there’s a new message, and after I read it the dot is gone. But the dot on the Facebook icon doesn’t seem to correspond to new posts or notifications, and doesn’t go away after I get on Facebook and look at some stuff. What could I do to make it disappear? And what does the dot signify on the Play Store icon, and how can I remove it?

I know that on my phone (Galaxy Note 9) the dots indicate a notification for those. I get them on the playstore when I have notifications indicating something is updating, pending an update, etc.

Facebook only has the dot when I have a notification at the top of the phone. Once I clear that, the dot goes away.

If you go to settings->Notifications you can change whether the badge shows the dot for all programs (or you can disable notifications for specific programs as well).

Okay, thanks for that. I now see that I have to touch on the notification (bringing up the whole notice), not just look at it. Facebook situation answered and solved.

Still haven’t figured out the Play Store thing, and would like to know how to get the dot off once it’s there, rather than prevent the dot from appearing in the first place.