Some layer effects probably some Filters as well(something like Lightning)

Seem like Outer Glow Effect to me..
CMIIW

What effect do you mean exactly?

Could be some kind of bloom.

Duplicate your original Layer
Set the Duplicate to "Screen"
Blur it (Gimp gaussian blur)
Lower the layer brightness, increase contrast.

to make light/glow effect on photoshop, you can duplicate layer then go to Filter>Gaussian Blur>Adjust the blur *blur layer via copy not the original layer.. or you can right click on layer, blending options, outer glow.. :)