The following description was prepared by William Gross:
From earliest times, man has tried to protect himself from misfortune by the use of objects which he considered holy or otherwise (e.g., magically) potent. Amulets and talismans are items generally worn around the neck or wrist, carried in a pocket or purse or hung on a wall. They are meant to protect or aid those who carried or wore them. The Hebrew word for amulet, kame‘a, has the root meaning "to bind". Jewish amulets are usually comprised of texts (either letters or graphic symbols) that are inscribed on some sort of material; some may also contain plant matter or precious stones. The texts of amulets usually include holy names that are believed to have the ability to affect reality, along with incantations summoning angels or other magical powers. For the most part, an amulet has a specific purpose: to ease childbirth, facilitate recovery from illness, improve one’s livelihood, and so on, but in the modern world many are also made for general protection.
One of the irregularly-shaped hamsas from the rural areas, this example is an almost rectangular shape, with three schematic fingers below. The bottom corners represent the other two fingers to complete the five. The red stone has amuletic power as does the crescent inscribed below it for protection. The eye is itself an antidote against the “evil eye”.The red stone was often used on amulets for woman who wished to become pregnant.
The hamsa (five, as in five fingers) is an amulet shaped like a hand. The hamsa is arguably the most popular form of amulet against the Evil Eye and is used in a large number of countries. Probably originating in Moslem Spain of the 12th or 13th century, it crossed the sea to Morocco and spread across North Africa to the Middle and Far East.