Nazar Boncugu in Turkish refers to a very traditional item in Turkey, it's a blue bead used as a talisman which is beleived that it would protect you against the evil-eye. The evil-eye superstition comes from very early times and it can be found in most of the cultures in the world. To prevent this unfortunate thing, Turks invented a blue bead which looks like an eye that looks straight back at the spell-caster. So this would guard you from any negative energy or from jealous looks of others for example.
Nazar bead is a huge tradition in Turkey, anywhere you go or any people you talk to can show you a bead in his pocket, or at home, or in his car etc. And if this Nazar bead is broken for whatever reason, it's beleived that it worked and protected you from some evil-eye that probabily you are unaware of at that moment.
The Nazar bead is usually made of blue glass, with white and yellow or white and blue again circles inside, that would be a typical Nazar Bonjuk. But there are other colors too, fashionable ones such as white color with blue circles inside. However, the blue is always the traditional color of this talisman. The Nazar bead has usually round shape, but it comes in all sizes and all kinds of shapes and decorations; sometimes as a keychain, or a photo frame, or a bracelet, with inscriptions, a refrigerator magnet, and so on. It became an art today, it's a part of the Turkish culture.
Nazar Boncuk doesn't have any religious significance, or it doesn't bring good luck, not a luck charme neither, it's just a pure belief against a superstition in order to ward off the danger of the "evil eye".