What are orbs of light?

Everytime you kill things with your super the killfeed says:

"[player] Generated # orbs of light"

They don't seem to be in my inventory anywhere or on the ground to pick up, what are they for?

It seems to be something related to co-op gaming.

From Destiny Wiki:

Orbs of Light are glowing balls of energy generated by other Guardians when they use their super abilities. Orbs can be picked up by any other player in the Fireteam, and provide a large boost to a player's super ability recharge meter.1 The super ability recharge boost when the player picks up an Orb appears to be larger than the boost that players receive from kills, time, or other actions. Orbs of Light do not appear to serve any other function, and are a cooperative gameplay mechanic designed to encourage players to play in Fireteams and reward them for working together.