Floaters are translucent specks that seem to float about in your field of vision.  Most people have some floaters normally, but they usually do not notice them until they become numerous or more prominent.  They become more apparent when you look at something evenly bright, such as white paper or blue sky, or looking through an optical instrument such as a microscope or binocular.  They are more common and seems to be more annoying to people who are near sighted.

Much of the interior of the human eyeball is filled with vitreous gel, a clear, thick substance that helps in maintaining the eyes round shape.  Light passes through the vitreous to reach the retina where images are formed.  Any bits of non-transparent tissue in the vitreous cast shadows onto the retina, and you see those shadows as something "floating" in your field of vision.  As your eyes age, the vitreous may become stringy, and the strands cast tiny shadows on the retina.

However, floaters are not always a benign condition.  They may come from old or new bleeding within the eye as in diabetic retinopathy or retinal tear. They may be the result of a disease that causes opaque deposits in the vitreous or of an ocular inflammation that causes cellular debris. They may also be a residual from an old injury. An through eye examination including a pupil dilated exam will reveal anything serious that need medical attention.  The sudden appearance of new floaters, sometimes accompanied by apparent flashes of light in the peripheral vision can be a sign that a vitreous detachment has occurred. On rare occasions, these same symptoms can be a danger sign that a retinal tear has occurred.  The sudden appearance of numerous floaters in people with diabetes also need immediate medical attention.  It can be a sign of retinal or vitreous bleeding caused by rupture of retinal vessels.  Laser treatment may be needed to prevent further bleeding.