what exactly is the Fylgja?

[Xiomara]

Hi All,
Anyone could elaborate upon what is the activating of the Fetch,or the Fylgja?
What i know is that in Norse Mythology it is a being which is connected somehow with the person,maybe something like the Genius of the Romans or the Nagual of the Aztecs.But i have read somewhere that it is a person of the opposite gender,like a soul mate.I have also heard that it is some kind of energy in your blood or DNA which can(must)be activated.
So,i would appreciate if someone could elaborate upon

Thanks

[Jenny Crow]

I believe that it's something like what most people would call a guide but there's a good explanation here: freya.theladyofthelabyrinth.com/?page_id=14

[Xiomara]

Thank you very much,Jenny!