Pulsing ring at the bottom of my screen

[AC Question]

There was a blue pulsing ring above my home button for a while and wouldnt go away until i locked my phone.
I have a Samsung A3
I wanted to know what it was so that it doesnt happen again

 

[Tim1954]

Did you have the charger plugged in at the time? Samsung has this animation when you first plug a charger in...