There are many different branches of Heathenry, most of them split up depending on which deities you work with and how you work with them. For instance you have Asatru (which is working with the Aesir) and Vanatru (working with the Vanir) and Rokkatru (working with the Rokkr), Lokeans (working with Loki), Odinists (working with Odin) and so on. There are a few forum posts explaining some of the different practices here.
Northern Tradition Paganism (the link to what Dothraki gave you first) is not technically Heathenry. It's more of an eclectic practice itself. Most of the workers from this group tend to be oriented towards the Rokkr and the Jotunfolk (giants).
It's a practice of following the Norse gods and honoring them in your craft. They aren't worshipped, but more honored. Also you give them offerings. There are a lot of different Norse magick types. This is a brief telling of Norse paganism.