What do the British Army's Intellience Corps actually do?

I've been looking at the different regiments i can choose when i finish Sandhurst, and i'm thinking about joining the Intelligence Corps as the idea of "Intelligence Officer" appeals to me, however that's just the idea, are these the guys that go undercover and gather human sourced intelligence, or are these the guys that sit behind a computer all day, looking at Satellite photography and decoding algorithms?