Ok so this may be confusing. I'm starting Skyrim now and I don't want to miss out on this thing I saw in the demo by picking the wrong thing(skill tree?)

Basically what it was is when watching one of the three demos released a while ago I saw that the character was in the cave and Todd said that they were using this perk or shout(not sure which) that aloud them to light a path to the active quest. Sorta like the navigation thing they put in dead space 2. Problem is I'm not sure if it's on a certain skill tree or is this a shout. Or maybe I heard him wrong. Anyone with any info on this please.

Ever since I have heard about it I've always wanted it. Thanks

its a magic spell. You can buy the book from a vendor.
I don't know if vendor stuff is random or not but you will have to look around.

The spell is Clairvoyance, you can buy it from a vendor. I'm pretty sure the Jarl of Whiterun's Mage has a copy.

Ok great thanks. So it's only a one time magic spell or once you buy it you can keep it.