Light Core

Light Cores are small spherical lights of white or cyan energy found within enemies. They show up in modern games where Sonic relies on action or boost gauges, after destroying an enemy, the Light Cores home into him (or his Boost Gauge on the HUD) and charge up his gauge. With it Sonic is able to boost.

Rings are also just as good at charging the Boost gauge.

Sonic the Hedgehog (2006)
They debuted in Sonic the Hedgehog along with Chaos Drives. Light Cores were founded by the company Rimlight in hopes for cleaner energy.

They can replenish a bit of energy to the Action Gauge while Chaos Drives restore the most. Incidentally Chaos Drives also appear as a Power Up on item boxes. Once the item box is busted it will fully restore the Action Gauge. Unlike Sonic Adventure 2 where Chaos Drives slowly fall to the ground and you pick them up, Light Cores and Chaos Drives home into you the moment the robots are destroyed. They are not used for Chao raising, as Chao gardens are not in this game.

Sonic Generations
While they are never referred to in any media as such, all enemines in the game are powered by orbs that resemble Light Cores. These power sources function similar to Hyper-go-on in Sonic Colours and along with rings can restore Sonic's Boost gauge when absorbed.