Physically, most Dryads could be mistaken for Elves. They are larger than Elves, both broader and taller, and decidedly more porportioned - Dryads are VERY female. Beyond that, little can be said. There are as many varieties of Dryads as there are species of Trees, but certain types of Dryads are especially representative of the Race, and are certainly the most common. There are large numbers of Oak, Maple, Apple, Aspen and Thorn Dryads. The Alliance of a Dryad depends on the tree they associate with.

All Dryads are spiritually linked to a cetain Tree - their HomeTree. Dryads are not Immortal, like most Faeries, but live only as long as thier HomeTree. This would be a much greater vulnerability were it not for Savantic disapproval of deforestation. As is, Dryads don't die accidentally.

Dryads maintain an ExtraMythic Space associated with thier HomeTree. They can at any time walk "into" their HomeTree, passing from visibility with no obvious door or Gate. Inside this Space they are utterly unreachable, though not invernable - the HomeTree can still be assaulted. Dyrads can bring others into thier Space, though this is tiring.
 

HomeTrees are connected with the Worldstree. When a Dyrad reaches the end of her Hajj, she finds that the Worldstree gives her access to her own personal Space, and, once Inside, she may thereafter exit from either her HomeTree or the Worldstree.  This is not an Instant Easy Teleport. Entering from Hometree and existing Worldstree (and vice versa) is very fatiguing and loses quite a bit of Time, though its passage is not experienced.

Naturally, quite a few Dryads are Savants. The fact that they can pop in and out of Worldstree at any familiar point is very Handy, and naturally they have an interest in protecting the Environs.