About Tattoos
A tattoo is a mark made by inserting pigment into the skin: in technical terms, tattooing is micro-pigment implantation. Tattoos may be made on human or animal skin. Tattoos on humans are a type of body modification, while tattoos on animals are most often used for identification.

Tattooing has been a nearly ubiquitous human practice. The Ainu, the indigenous people of Japan, wore facial tattoos. Tattooing was widespread among Polynesian peoples, and in the Philippines, Borneo, Africa, North America, South America, Mesoamerica, Europe, Japan, Cambodia and China. Despite some taboos surrounding tattooing, the art continues to be popular all over the world.
 
The word "tattoo" is traced to the Samoan word tatau, meaning to mark or strike twice (the latter referring to traditional methods of applying the designs). Sailors traveling the Pacific who encountered Samoans, and who were fascinated by the Samoan tatau, mistakenly translated the word "tatau" into the modern tattoo. In Japanese the word used for traditional designs or those that are applied using traditional methods is irezumi ("insertion of ink"), while "tattoo" is used for non-Japanese designs.

Tattoo enthusiasts may refer to tattoos as tats, ink, art or work, and to tattooists as artists. The latter usage is gaining support, with mainstream art galleries holding exhibitions of tattoo designs and photographs of tattoos.

Tattoo designs that are mass-produced and sold to tattoo artists and studios and displayed in shop are known as flash.

History
Tattooing has been a Eurasian practice at least since Neolithic times. Mummies bearing tattoos and dating from the end of the second millennium BCE have been discovered in Xinjiang, West China. Tattooing in Japan is thought to go back to the Paleolithic era, some ten thousand years ago. Various other cultures have had their own tattoo traditions, ranging from rubbing cuts and other wounds with ashes, to hand-pricking the skin to insert dyes.

Purpose
 Religious themeTattoos have served as rites of passage, marks of status and rank, symbols of religious and spiritual devotion, decorations for bravery, sexual lures and marks of fertility, pledges of love, punishment, amulets and talismans, protection, and as the marks of outcasts, slaves and convicts.

Today, people choose to be tattooed for cosmetic, religious and magical reasons, and as a symbol of belonging to or identification with particular groups (see Criminal tattoos). Tattoos of favorite bands and football teams' logos are fairly common in the west. Some Maori still choose to wear intricate moko on their faces. In Cambodia and Thailand, the yantra tattoo is used for protection.

People have also been forcibly tattooed for a various reasons. The best known is the ka-tzetnik identification system for Jews in part of the concentration camps during the Holocaust. European sailors were known to tattoo the crucifixion on their backs to prevent flogging (since it was a crime to deface an image of Christ).

Tattoos are also placed on animals, though very rarely for decorative reasons. Pets, show animals, thoroughbred horses and livestock are sometimes tattooed with identification and other marks. Pet dogs and cats are often tattooed with a serial number (usually in the ear, or on the inner thigh) via which their owners can be identified. In Australia, the symbol F is tattooed in the ears of cats and dogs to indicate that they have been neutered. Also, animals are occasionally tattooed to prevent sunburn (on the nose, for example). Such tattoos are often performed by the veterinarian him or herself and in most cases, the animals are anaesthetized during the process. Branding is used for similar reasons and is often performed without anaesthesia, but is different from tattooing as no ink or dye is inserted during the process.

When used as a form of cosmetic surgery, tattooing includes permanent makeup, and hiding or neutralize skin discolorations. Permanent cosmetics are tattoos that enhance eyebrows, lips (liner or lipstick), eyes (shadow, mascara, liner), and even moles, usually with natural colors as the designs are intended to resemble makeup.
info provided by wikipedia.org