An eye that sees well without spectacles is the right length and therefore light falls onto the retina where the image is processed by the brain to form a clear picture.
A short sighted eye is usually too long and the image focusses in front of the retina, rather than on the retina, causing a blurred image.
A minus correction is needed to correct the problem. If you have a -2.00D spectacle prescription for example, then you are short sighted.
Permanent solutions to the problem are also available, including LASIK and LASEK.
Phakic IOL's are also available for people who are very short sighted.
Myopia means short sighted.
People who are short sighted can see objects close up but cannot see in the distance.
Many people cannot read or use a computer without spectacles because the distance at which they would focus without spectacles is too close for comfort.
Generally, short sighted people would need spectacles for most things including driving and computer work, but some maybe able to read or thread a needle without specs.