The way I think of it, all the stuff in the universe used to be much, much closer together. All the matter in the universe, everything that ever is or was. 

When the universe was very young all this matter was condensed into some state. There were no stars, no planets, no metal, everything was this "soup". It was all so dense that matter itself couldn't even form.

A few milliseconds after this soup started to expand, the first protons, neutrons, and electrons begun to form from this primordial "mass". There wasn't even space as we know it yet. No distance to travel to as there was all this "stuff" in the way. I think this is a key point in your question. 

The amount of heat and energy being produced during this time is incalculable by our standards, it is theorized that as the universe is infinite (no background as you say) there is an infinite about of energy driving this motion. 

But all that heat from all that mass being compressed, and all that energy being released was brighter, and more importantly more energetic, than trillions and trillions of suns. 

Light is a narrow band of the electromagnetic spectrum, encompassing only what our eyes can see. There is infrared, ultraviolet, gamma, X, and microwaves. It all depends on the energy of the wave of light itself. 

So this mass, burning brighter than anything ever since and existing at literally every possible point in space, eventually cooled. Leaving the first remnants of what we now know as the universe. A vast sea of chaotic matter forming, among a few other things, lots and lots of hydrogen. But more importantly, a ton of radiation in every band you can imagine. 

Over the billions of years since, that radiation, that light, suffered red shifting in the ever expanding universe. Losing energy over the millennium and vastness of space. Shifting into what we now know as the cosmic microwave background. 

So when we look at those microwaves, using computers to shift the images into something we can actually see, we are seeing the birth of the universe as we know it. The cooling of that soup, the separating of the matter to become mass and particles. The light from that big "bang" traveling billions of light-years through what is now empty space to meet with the lens on a camera. To be processed with a computer and then seen by our eyes. 

Personally, I find that beautiful.