As your character travels through the world, he may learn new runes that you can add to your Runebook, which is in your character sheet.
When you find or learn a new rune, add it to your Runebook as a word in italics, for example: fragility. A rune is a symbol representing a word that spirits have a connection to. So you can learn runes such as "fire", "water", "iron" and others. A fire spirit will react in a certain way with a fire rune, just as a water spirit would react differently to a fire rune.
You can combine runes in strange ways to form powerful links.
Ultimately, runes are a roleplaying tool, and you can come up with ideas in what ways to use them as you see fit. The people of Havsgard put runes on their ships that let spirits inhabit the ship to guide them, for example.
Runes can be powered by blood. Your success at reading and using runes will be tied to your Runes skill.
An example of an item you could make with runes: A BloodstoneEdit
Bloodstones are stones covered in special runes which store magical energy, so when you are in a tight spot, you can 'refill' your magical energy and continue fighting. Or you could use the bloodstone for a quick healing spell. Larger and more powerful bloodstones could have more imposing and interesting uses.