That means the gel inside my eye has become watery rather than a thick gel, slightly collapsed and pulled away from the retina (which causes the retina to send help signals to the brain hence the flashing). It will happen to about 75% of us, usually around 65 - I am quite a bit younger than that but hey, these things happen!
The floaters are dead cells clumping together in the thinning gel, being pushed together in the decreasing space. He says my retina is fine, I have nothing to worry about and as the flashing is now disappearing, the brain will learn to ignore the floaters.
So, all that is good news.