Humans, Elves, Dwarves, and Halflings were the first intelligent races in the world. All civilization started with them. From the balance of the planes came reflections of these races and their civilizations. In the Fey Wild four races also developed: Changelings, Eladrin, Goliaths, and Gnomes. For the Shadowfell it was Werefolk (Shifters), Drow, Minotaur, and Shades. Some of these other planar races crossed the barrier and settled in the world eventually blending into society as one of its many oddities.
Humans found that they could breed with Elves, Eladrin, and Drow to make a Half-Elf or with Dwarves to make a Half-Dwarf (Mul). These sub races resemble a blend of their parents, but are unable to make more of themselves. Half-Elves can breed with any of the races that can make them, but always produce an offspring of that race as if they were one themselves. The same goes for Half-Dwarves.
When the Gods started to interbreed with the races it caused demigods to appear. Even though the gods are cut off from the world demigod blood can surface anytime in the bloodline. Demigods (Deva, Tiefling, Genasi, Shadar-kai and Githzerai) can all claim divine ancestry. Verasha’s bloodline can produce a unique form of demigod (Vryloka).
Using various forms of magic, the Golemkind (Warforged) were created. Primal and Psionic magics were able to create variations of the Golemkind. Primal Golemkind (Wilden) are plants linked to the Fey Wild. While Psionic Golemkind (Shardmind) are crystals imbued with consciousness.
After the Darkening, and souls could no longer travel through the spirit realm to their final resting place, undead populations grew. Sometimes one of these undead will have a soul so strong that the person rises as a Revanant.