Most spiders have eight eyes, though some have six or fewer. In spiders that possess multiple pairs of eyes, the main pair of eyes are usually in the middle of the head and directed forward. The other pairs are specialized for different vision tasks.
For example, in jumping spiders, the eyes on the edges of the main pair are tasked with detecting movement. They have excellent peripheral range, but they are not good at discerning detail. The pair of eyes closer to the main pair provide depth perception. The main pair of eyes provides clear, focused vision, possibly in color.
Other kinds of spiders, such as wolf spiders, have eyes specialized to reflect light for hunting in low-light conditions. The different groups of spiders often have very different arrangements of eyes on their heads, depending on how they hunt. Some species of spider lack eyes entirely. Spider eyes, unlike insect eyes, are simple and do not have multiple lenses.