LDR doubt

Could you please explain me why if I cover the LDR i’ve got more tension (voltage) at white cable.

The energy flows from red cable, pass through fixed resistor and after the LDR and ends at the ground (I imagine).

When you cover the LDR, it’s resistance increases and as it is part of a voltage divider with the fixed R the voltage at the junction increases.

Weedpharma

The energy doesn't actually flow through the cable(*) but that's probably confusing at this stage. All you need to know is Ohm's and Kirchoff's laws at this stage. V=IR for each resistance in the circuit, currents sum at a junction and voltages sum round a circuit.

(*) A deep understanding of Maxwell's Equations is needed really, but if energy did flow through the cable you would expect more power to be dissipated at the end of the cable nearest the power source, but in fact power is dissipated uniformly along the wires.