Glowing green cards

So I started playing about a month ago and am loving the game. I have answered all my question through playing except one.

What are the glowing green around certain cards. I can see it either when going into my collection or updating my decks but not during play 

Thanks in advance 

DarkDivinr 

 

I usually see glowing green cards on the "Resupply cards" screen after an adventure.

In this case, this is because they were newly acquired during the adventure. It helps to quickly identifying cards out of your primary deck. On the other screens, honnestly i didn't paid attention on that before. I suppose that's for the same reason : new cards.