The Paleozoic Era also is the start of the Phanerozoic Eon (543 mya to present), but this era lasted only about 300 million years. This era was characterized by the rise and fall of the sea level several times, which allowed shallow waters to cover the continents several times and marine life to flourish.
The Paleozoic Era began with the development of shells, which allowed fossilization of these organisms to occur. This is why there is much more known about the Paleozoic life than Precambrian life.
One of the major developments in this era was the formation of Pangaea. This era was characterized by the major movements of the plates - plate tectonics. Scientists believe that this movement caused the rise and fall of the sea levels.