What are the shielding effects of shielding boxes?

Shielding effect:
A: It is to limit the radiated electromagnetic energy inside the equipment beyond a certain area, that is, to absorb internal interference signals;
B: It is to prevent external radiated electromagnetic energy from entering a certain area, that is, to shield external interference signals
Shielding concept: When the simulated interference source is placed outside the shielding box, the ratio of the electric field intensity, magnetic field intensity or power at a certain point in the space before and after the shielding box is placed is then logarithmically (lgp1/p2), expressed in dB.
C: Testing equipment: network analyzer, signal generator, spectrum analyzer, dipole antenna, horn antenna, shielding box.