Floaters are common. They are small "bug-like" interferences in vision which you may notice intermittently or on a constant basis. Floaters are caused by a jelly-like material, the vitreous humor, in the eye. A floater casts a shadow that you see. Due to the gel-like material inside the eye, these shadows can float and move around. Floaters are most noticeable when the pupil is at its smallest. Therefore, you may see them best looking at a bright background such as a white page or a bright sky.
Floaters in themselves do not threaten the eye's health. Since the vitreous humor interfaces with the retina, it is important that you see your eye doctor when you notice new floaters or an increase in the number of floaters or the increase in the frequency in which they see floaters in their vision.
Flashes of light often are associated with floaters, and they may represent possibly a more serious problem in the eye. Flashes of light can be caused by the tugging of the vitreous on the retina and therefore cause retinal breaks or tears. Flashes of light can also be caused by neurological problems which have nothing to do with the vitreous of the eye. One example is ophthalmic migraine. Flashes of light are a serious symptom and should be addressed by your eye doctor immediately.