Ok. I'm not going to type a lot but you have to understand that any point out of the primary plane of focus will be rendered on the film or sensor as a circle. (Look up Circle of confusion.)
Therefore even microscopic particles such as dust, ash, ice etc. if closer to the lens than the plane of focus and outside the area of acceptable depth of field, (Another to look up.) will gain the appearance of circles in the image.
If these particles are strongly lit, for example by the camera's flash unit, then they will appear as "glowing" circles or even "orbs".
Simple to explain, even simpler to recreate. No supernatural explanation needed.
But I have no doubt you will choose to believe whatever you want to believe...
There seems to be a whole tribe of people that refuse to accept this simple explanation and I'm quite sure David Icke is one of them...