SRD:Holy Symbol

Holy Symbol, Silver or Wooden
A holy symbol focuses positive energy. A cleric or paladin uses it as the focus for his spells and as a tool for turning undead. Each religion has its own holy symbol.

Unholy Symbols
An unholy symbol is like a holy symbol except that it focuses negative energy and is used by evil clerics (or by neutral clerics who want to cast evil spells or command undead).