Before working with project like this, that use high voltage, take serious precautions, because 230V is lethal. Now lets get to the circuit, which is not much of a circuit, just 2 resistors, 1 capacitor, 1 diac and the LED. The capacitor charges by the diode and the resistor. When the voltage on the capacitor achieves 30V the diac “releases” the electrical tension and the capacitor empties thorough the diac, LED blinks. The blinking time depends on the capacitor. There are various applications for this circuit, most in signaling something, but its not always necessary to use 230V so i would suggest not using this circuit unless its necessary.
Blinking LED at 230V: [Link]