It is generally believed, and some will claim to have proved it, that the tree can be entered from select points on every plane; these points are called "gates." Once a gate is passed through, the tree ~ which appears to be actual, growing wood, variously describes as a yew tree or an ash ~ can serve as a conduit along which creatures can travel. All branches slope, so that a traveller can move "down branch," towards a limb and ultimately towards the trunk, or "up branch," towards its ends. It is possible to leap from the end of one branch, across a gap, to another branch, and thus potentially gain access to anywhere. However, rarely would a traveller have a map that would enable them to know which branches to leap to ~ and it would be very difficult to return along the same path, not knowing for certain which branch was leapt from.
The wood, bark and leaves of Crann Bethadh have value to alchemists, but are only ever collected (or needed) in small amounts, no more than an ounce. There is danger that any more and the local tree will "shudder," throwing off any who are standing on its branches, potentially to fall forever into nothingness if not successfully catching hold of a random leaf or twig.
It is acknowledged among many pagan religions that the late-comer Christians, embracing the Latin and Celtic crosses, were really just adopting an earlier symbol meaning to depict the Tree of Life. Thus members of underground pagan sects in the middle east and central asia continue to use the cross as a symbol, though it has nothing to do with the crucifixion.