The word pelasgian means from the sea. It also means hairy. And to top it all, it means springing from the earth... sticks embedded in the earth that spring up in human form to populate their surroundings. From this we can conjure up a race of people that came from the sea, wore beards, and were "indigenous." Hence, they were the aborigines who settled the Pelaponnesus, coming before the Dorians. One might say they were the aboriginal ancestors of what we now call "Hellenes" -- today's Greeks as they have come down through the ages.
The Pelasgians were successful in establishing themselves and their culture in the land and sea. Apparently they espoused the existing cult worship of Hera, as there is still to be seen the ruins of a Temple dedicated to Hera which they built. They are credited also with being admirable house builders, taking a different approach from the old, cramped design. Instead of a hut, they used large stones for the base making a drier, more lasting habitat, which was quickly adopted by their neighbors.
They remain important in the grand sweep of Greek pre-history. Some ancient myths are even said to have begun with them. The myth of Helios' harnessing the sun to his chariot is said to date back to the Pelasgians.