Yes - at its most basic - a pickup collects
vibrations from the strings - and to a lesser extent the bridge
and body of a bass and converts them into electrical signals
that can then be fed to an amplifier or other output. The element
that collects and converts these signals is a "transducer".
One of the most common types of transducer used for acoustic
instrument pickups is a "piezo" model - typically "piezo
Piezo sensors accurately detect small pressure changes, so are
ideal for responding to vibrations from the strings. "Ceramic" refers
to the material - usually metal oxide sheet - in which the sensors
are embedded. Pickups can also be "active" or "passive".
Active pickups have a very low power output, so generally require
preamplification to add an extra 'boost' to the signal
before it is passed to a standard amplifier or PA system. Passive
pickups have a more powerful output so do not require preamplification.
In some cases however - this can reduce the quality of the tone