The OR gate is a logic Boolean gate that represents addition in basic algebra. If either of the inputs or both inputs to a basic OR gate are forced to logic HIGH (1) the output is forced to logic HIGH (1). If both of the inputs are forced to a logic LOW (0) the output is forced to a logic LOW (0). This closely resembles the addition statement where only Boolean variables are allowed. The symbol and truth table for an OR gate can be seen here.