Who is Daneel Olivaw from Foundation and Earth and what is their importance?

Daneel is the robot that greets Travize and his friends once they arrive on the moon. It's Fallom who recognizes that he is mechanical, though he has to tell the others that he is robotic. It's Daneel who tells them that he engineered the people of Gaia in an effort to unite humanity, making it easier for robots to determine what was and was not harmful to humanity as a whole. Daneel tells Travize that he helped them along their journey and that he has a reason for drawing them to him - that Daneel himself is "dying."