A XNOR gate, like the XOR gate, is also referred to EXCLUSIVE NOR. With the XNOR gate the output is forced to logic LOW (0) when one of the inputs are exclusively forced to logic HIGH (1). If both of the inputs are forced to either logic LOW (0) or logic HIGH (1) the output is forced to logic HIGH (1). This is similar to the XOR gate but is inverted. The symbol and truth table for an XNOR gate can be seen here.