What is the Phillips screwdriver and why is it named Phillips?

That crosspoint, with side fillets, was designed by the Phillips company, the company of Henry F. Phillips, the founder. The screw head is named after them. Phillips found this shape of drive head provides an easy method of aligning/centralizing a screw onto a driver bit on production lines. It was also an early attempt at security. A link is provided to the Wikipedia article on Mr. Phillips, and a picture of the head of the fastener that bears his name can be seen there.