Measured in dBspl. It quantifies the intensity of sound pressure at one metre's distance from the loudspeaker when an electric signal of 1 Watt is applied to it. For example, 93 dBspl/m/W indicates that in the aforementioned conditions a sound pressure of 93 dBspl was measured.
Measured by two quantities. Peak power is the maximum power the loudspeaker can handle without being damaged. If even once the signal goes beyond this value the loudspeaker will be damaged. The RMS power (Root Mean Square) is a unit that measures the average applicable power that can be applied for an amount of time before the heat begins to damage the loudspeaker.