The 18 mm width (1 modular unit) means it occupies one slot in a standard consumer unit or distribution board. Rated IP20 once the distribution board is installed and conductors are connected; that's fine for enclosed panels but not for wet environments.
The 30 mA residual current sensitivity provides supplementary protection against electric shock for AC sinusoidal fault currents (Type AC). Neutral conductor is not switched by this variant, so the neutral bar stays continuous through the device. Touch protection is built in.