It's called GDDR5 and it was not specifically made for the PS4. It's been around for a long time. GDDR5 offers a high bandwidth which is great for graphics, but has a high latency which makes it not ideal for computing. DDR3 offers a lower bandwidth but also has lower latency. Which is why computers use it. PS4 uses GDDR5, high bandwidth and high latency Xbox One uses DDR3 and also uses eSRAM to help make up for the lower bandwidth while maintaining the lower latency.