Why did Facebook spend $2bn on virtual reality?

Facebook has announced it will buy Oculus VR, a Californian company which specialises in virtual reality products, for around $2bn (£1.2bn).

The company's flagship product, the Oculus Rift, is a goggle-like "immersive" headset for video gaming.

But what now makes virtual reality so important to Facebook and a host of other businesses? Rory Cellan-Jones reports.