The floaters come from the retina in your eye.... They may have black dots in them, and those are more serious than the transparent ones.(the black dots are blood spots). They do not reside in your brain.

The general rule is when too many floaters come all at once, it MAY be a signal that you are in for a detachment of the retina.

However, nearsighted people tend to have more of them than normal sighted people because the eyeball is oval in that area and not round. This tends to put pressure on the cells and they may slough off more frequently.

Anyone with a huge flood of floaters should see an eye doctor ASAP. (especially if severely nearsighted.)

If your tears are not forming correctly you may notice thickening of the tears, which seem to "float" over the eyeball as well. Using artificial tears may help this. People in hot dry climates may have dry eyes occasionally. Make sure you keep hydrated, drinking enough water daily for your needs. Dry eye is more common in older people, and less so in young people.
It can be a sign of conjunctivitis, pink eye, or other inflammations of the surface of the eye. So seeing an eye doctor would be a good idea for this too.