During their millennia of existence, the Eldar spread across the galaxy and colonized many planets. There are three main types of Eldar Worlds: Crone Worlds, Maiden Worlds, and Exodite Worlds.
Crone Worlds are the original homeworlds of the Eldar. Unfortunately, they're all located in the Eye of Terror, and are subject to the usual effects of planets exposed to Warp energy. In short, they're Daemon Worlds. Unfortunately, they are also the only planets where one can find spirit stones, which will protect an Eldar's soul from being consumed by Slaanesh upon death. As a result, Craftworlds will send suicidal sorties into Crone Worlds to gather spirit stones.
They are named after Morai-Heg, the Crone Goddess and Eldar Goddess of Fate.
Maiden Worlds are worlds which were terraformed by the Eldar millennia ago. Note that these planets were not instantly terraformed like Imperial worlds, but were selected and seeded with simple bacteria to create breathable atmospheres, while Eldar planet life would be introduced. This terraforming process was natural, and would take thousands of years to achieve, with only future generations of Eldar enjoying them. When the Fall of the Eldar occurred, many Eldar that didn't fleet in Craftworlds went to Maiden Worlds. Unfortunately, many Maiden Worlds were subsequently colonized by humans during the Great Crusade, and many Eldar don't take kindly to the mon'keigh squatting on their planets.
Maiden worlds are known as Lilaethan after Lileath, the Eldar Goddess of Dreams.
Exodite Worlds are planets which were settled by the Exodites when they abandoned the Eldar Empire. They are highly savage worlds, and Exodites will only build a few settlements, many of which are temporary. Most of the wildlife on Exodite Worlds are dinosaur like creatures which the Exodites call "dragons", and are usually predatory.