"Precious gems and metals make excellent foci for magical enchantments. Although most of the knowledge of creating such talismans has been either been long lost or is jealously guarded by the Eastern mage clans, rings and amulets of power may still be discovered. The primary drawback of enchanted jewelry is that multiple pieces seem to interfere with each other. For this reason, only one ring may be worn on each hand, and but one amulet may be worn about the neck. The greatest advantage of rings and amulets is that they are nearly impossible to strike in combat, and as such do not need to be repaired or maintained as armor does."

Diablo I Manual(src)

Jewelry is a common combined term for the Amulets and Rings in all three Diablo games.

In Diablo II, Jewels and Charms are also sometimes considered jewelry, though jewels are actually also jewelry.