how to "follow" sites.

i am trying to understand the "following" and "unfollow" button in the admin bar.

this button (screenshot) is in my admin bar, so it seems i will "follow"/"unfollow" myself.

it seems to me that this only makes sense if i visit another site on the network that
1- i am a member of that site &
2- they have their WP admin bar visible.

Please explain the difference between displaying the follow button on the front end, back end & both.

kind regards,