What makes trail shoes so much better than normal running shoes?

I recently tried a pair of Mizuno Wave Daichi trail shoes for some fell running in the Lake District.
I had run there in regular trainers last September and the difference in grip and comfort was night and day.
I caught up with Mizuno's UK Marketing Manager Graham Johnson at Wasing Park - site of next month's Endure24 - to find out more about the technology that makes trail shoes so different to my regular road shoes.