Faerie Land exists in Lower World. It is also known as the Faerie Realm or Realm of the Fae. However it should be cautioned that Fae do not like being called Faeries. They much rather prefer “the wee folk” or the name of the type of Fae that they are. It isn’t wise to call, say, an redcap, “wee”.
Fae can have one of three alliances. To the Seelie Court, the Unseelie Court, or to themselves. Fae aligned with the Seelie Court are usually believed to be more benevolent, though this is not always true. Fae who are with the Seelie Court would rather help a human than hurt them, which is what separates them from the Unseelie Court. Fae aligned with the Unseelie Court would rather harm a human than help them. However, this isn’t to say that the Seelie Court is good and that the Unseelie Court is bad. That would be a blanket statement, which is bad. They have an equal chance of being good or bad, but they don’t go about things the same way.
Lastly is the Solitary Fae, who are aligned to themselves. They are usually either Fae banished from one of the Courts or who choose to remain neutral because they do not wish to fight. The Seelie and Unseelie Courts are constantly at war with each other.
From Samhain to Beltane, the Unseelie Court has reign over the realm of the fae. A warmer than normal month during this time means that the Seelie are winning the war. From Beltane to Samhain, the Seelie Court has reign over the realm of the fae. A colder than normal month during this time means that the Unseelie are winning the war.
The basic structure of the Seelie Court has the Seelie King and Queen at the top, their children below them. Below the Seelie Princes and Princesses comes the Seelie Knights. Below the Knights are the Changeling Caretakers. And finally, the rest of the Seelie Court is below that. The Unseelie Court has a similar structure, except that there are no Changeling Caretakers. It is rumored that aside from the Unseelie royalty, Unseelie Fae cannot reproduce.
It is my speculation that they can reproduce, but their children are killed shortly after they are born. This can be backed up by Unseelie Faeries continuing to exist and grow in number. To be precise, it is my belief that they swap their children with human children and then, unlike their Seelie counterparts, kill the human child. Whether or not this is accurate, I can’t be sure for certain. It isn’t really a good idea to talk to an Unseelie alone, and most wise spirit guides will not go with you, and advise against you going into, Faerie Land.