But what do they sell?

Ok, it's Hollister and they sell clothes and stuff aimed @ 'young' people :-)
You'd never know that from the shop front though.
It's a pretty impressive window display made up of lots of screens depicting 1 moving image of an ocean scene with crashing waves and surfer dudes.
More of a lifestyle brand and maybe also a spin-off of the original cool outdoor lifestyle brand Abercrombie & Fitch (A&F).
Anyway, it's great to see on another dreich Monday evening in Edinburgh!