I made a fluctuating circuit that controls an LED to be on or off, How does it work?
Your diagram is too small and fuzzy to read the text.  But the two cross-connected transistors in the center form an astable multi-vibrator circuit. Essentially a low-frequency, square-wave oscillator.

The transistor in the lower left corner forms a driver which controls power to the LED in the lower right corner.

Corrected: Thank you Ignacio Vazquez-Abrams for pointing out that it is an A-stable multi-vibrator (one with no stable state, it continuously oscillates)