Facebook Messenger - Need good explanation of icons

[peachykeenx5]

Hi! So glad that I found this forum. Have been looking around the web and kept finding info that contradicts itself with the Facebook Messenger/Icons

So, here goes......

Does a "friend" show up as a green dot if they are ACTIVE on the Facebook Messenger App (fyi, there is no desktop involved, fyi...the apps are on the iPhone...Facebook and Facebook Messenger)

Or, do they show up as a green dot because they have simply opened the Facebook App (not messenger)

When said green dot switches to the mobile phone icon, does this mean the "friend" is now actively using the Messenger/Chat on Facebook Messenger App - Like you watch it change before your eyes kinda thing....one second it's the green dot, the next it is the mobile phone icon with the 1m next to it.

If you then click on the "friends" name...under the name it will say "active 16m ago"

and, on the other hand....in your "friends" list it will say like 15m to the left of the mobile phone icon

does that mean they are on the messenger app or on the facebook app

or both?!

How can a friend show up with some amount of time next to the mobile phone icon and then when you click on their name, it DOES NOT show "active X mins ago"
How did they change this setting when before you could see their name and how many minutes ago they were active....

Sorry so many questions!!
Thanks for any help!!!