The 556 consists of a pair of 555 timers in one package. The two timers work independently and only share common power supply connections.
A typical example of a 556 circuit is shown here. The circuit drives a piezo sounder to provide a pulsed bleeping sound (similar to the reversing warning on many vehicles). One half of the 556 is running at the resonant frequency of the piezo sounder, around 3-4KHz, while the other half is running at a very low frequency of about 0.5Hz. The output from the low frequency oscillator is connected to the reset pin of the high frequency oscillator to modulate the output and turn the bleep on and off.