Sensativity?

Here's the definition:

Sensitivity: A measure of the acoustic output of a loudspeaker resulting from the application of a fixed input power. Most often, sensitivity is measured in decibels at a distance of 1 meter from the source with 1 watt of input power (dB 1W/1m). It is also seen as dB at 2.83V/1m, which allows a better comparison of sensitivities regardless of load impedance. 2.83V is the amount of voltage necessary to deliver 1 watt of power into an 8-ohm load.

To answer your other question, yes, a higher sensativity rating generally means more output power (louder) for a given input.