This post is the beginning of my quick (layperson's understanding) explanation on the various factions, worldbuilding, and characters of the Warhammer Fantasy setting; commonly called 'The Old World.' I'll be doing these to help lay a groundwork or foundational set of knowledge as I understand it before I talk about what I would do differently, what the neat parts about the existing lore are, and anything else where knowing my base understanding may help or enlighten.
The first group I want to bring up are the Wood Elves or Asrai. The Wood Elves are a branch (hehe) of Elf that have splintered (hehe) off from the Elves of Ulthuan (to be covered more when discussing High Elves, Dark Elves, Chaos, and such) largely as a result of an ancient pact between Elves and forest spirits.
As I understand the lore, Forest spirits are similar enough to demons in The Old World but are bound or tied to woodlands. Places where travelers become lost forever amidst twisting pathways where time works differently. They are not necessarily as malicious as demons, but much like other spirits and similar entities; forest spirits are imbued with their own branches (hehe) of the winds of magic.
The Wood Elves came from Elven colonists who were settling in these woodlands long before anyone else lived in these places. Their bond with the forest angered some of the forest spirits, but they have been accepted and now live in harmony with the forest. This means they hunt, gather, only use fallen wood or their woodsinging for wood crafting, and upon death their bodies and spirits/souls are sent into the woods in a cycle of Life, Death, and rebirth.
I'll go more in depth on magic in the setting later, but for now I want to comment that they do definitely practice magic, have specific gods that they follow and generally (despite Total Warhammer's factions listed) really only live in the large forest of Athel Loren or the smaller forest of Laurelorn.
Wood Elves, as all Elves; are generally more resistant to the influences of Chaos than humans are. So, the manipulations of the forces of Chaos happen more subtly. In the Wood Elves, this is represented by isolationism and paranoia. The defense of their forests is their primary goal as a faction, and they rarely send forces out unless it is going to help the protection of their woodlands homes to some degree.
This has been my rambling treatise on Wood Elves from a basic level. As with most of what I know on Warhammer, it's derived from several fan wiki sites, forum discussions, video games, and the few novels I have read. If anything is super wrong or a gross oversimplification, feel free to message me or reblog and add to my knowledge.