Warriors is a book series written by Erin Hunter. It is about four Clans  of wild cats (ThunderClan, RiverClan, WindClan and ShadowClan) living  and surviving together. We each have our own territories around a great  lake. We used to live in a huge forest, but we were driven out by  Twolegs. (You'll have to find out more by reading the books). 
Anyway,  around the lake each Clan has a territory specifically for them. It is  mainly filled with each Clan's preferred source of food. My Clan prefers  things like birds, mice and voles, RiverClan likes fish and watervole,  ShadowClan likes pretty much anything (even toads and frogs, eww!) and  WindClan likes rabbits.
This is a very rough description of each  Clan's territory: RiverClan has a river and most of the forest to the  west. Their territory begins where the Clans rested at the end of the  Great journey, and ends at a ThunderPath (a road). Then from the road  onwards is ShadowClan territory, a forest of pine trees. Their territory  ends at a place where Twolegs go in Greenleaf (Summer). At the edge of  the clearing my Clan's territory (ThunderClan) begins, and it ends at  the edge of a stream. We have normal forest with a variety of  vegetation. On the other side of the stream, WindClan has it's domain.  Their territory is just moorland, stretching until it ends at the  Horseplace (Stable). We each have our own camp, where the Clan eats,  sleeps and dominates.
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| This is a map of the Clan's territories | 
Each Clan follows the guidance of StarClan.  StarClan is the place all cats go when they die. (Well except for evil  ones, like the legendary Tigerstar, but you'll have to read about him in  the books. They go to a place called the Dark Forest. Unlike StarClan,  Dark Forest cats cannot interact with each other. However, they have  found ways to interact with cats that are living. *Gasps*.) 
Anyway,  back on track. StarClan sends signs of things to come and prophecies to a  special cat in each Clan. This cat is the medicine cat, and it is in  charge of interpreting these signs and healing its Clanmates. Each half  moon the medicine cats meet at a sacred place to share dreams with  StarClan. This place is the Moonpool.
The leader of a Clan can also  get signs, but this is not common. Each new leader must travel to the  Moonpool and recieve nine lives from StarClan, as well as take the name  'star'. (For example, Firestar). Leaders and medicine cats are not  allowed to eat before or while traveling to the MoonPool. Leaders of a  Clan must appoint a deputy before moonhigh the day they return from the  MoonPool. This special cat is to be the leader after the current one. A  cat MUST have mentored at least ONE apprentice to be a deputy. If a  deputy dies, the leader must then appoint a new one before moonhigh once  again. When a leader loses all its nine lives, the deputy takes its  place. 
When a cat dies and its spirit goes to StarClan, the body is  mourned by the cats of a Clan for a whole night. Once dawn comes, the  elders (or retired cats of a Clan) take the body and bury it. Elders are  well respected within a Clan and often tell great stories of long ago  battles and times.
Now, to defend and hunt for the Clan, the Clan  appoints warriors. Warriors are cats that have completed combat training  and are skilled enough to hunt. A warrior must always hunt for the Clan  before himself/herself, even when they are not on a hunting patrol.  They make sure the Clan's borders are secure and they defend it from  threats such as other Clans, foxes and badgers. When they are  experienced enough, a warrior may take an apprentice appointed to them  by the Clan leader.(Sadly, I am not experienced enough just yet, as I  have only been a warrior for a moon (a month), though I am already one  of the best fighters!) An apprentice is a young cat over six moons old,  in training to become a warrior or medicine cat. Each one takes the name  'paw'. (For example, Sorrelpaw). It is trained by a warrior or medicine  cat, and the cat training the apprentice is called its mentor. Each  apprentice must make a trip to the MoonPool sometime in their training.  All apprentices must perform duties like fetching food for the elders,  changing the bedding in the dens and helping the elders to remove their  ticks. When an apprentice completes its training and receives its  warrior name it must guard the camp alone the night of its ritual. It is  not allowed to speak.
Baby cats, or kits, stay in the nursery and  are not allowed to become apprentices until they are six moons old. They  are looked after by their mothers, the queens. The queens are she-cats  expecting or nursing kits. Right now I don't have any kits, and I  haven't found anyone special in my Clan yet. Oh well, I can wait.  Anyway, a cat is not allowed to take a mate from another Clan. This is  seen as betrayal and can result in serious consequences.
Whoops, back  on track. Every full moon, the Clans meet at a sacred place in a brief  truce called a Gathering. Only a few of each Clan are selected to go,  while the rest guard the camp. Here elders share stories of old times,  leaders make decisions affecting everyone, and news from each Clan is  shared. If the Clans break the truce, StarClan gets angry and they will  send clouds to cover the moon. This usually ends a Gathering  immediately. 
Twolegs are big problems for Clans as they are big,  loud, lumbering creatures that trample vegetation and scare away prey.  They have huge monsters (cars) that reek and can kill cats if they hit  them. The monsters hardly ever come off the Thunderpath (a road) though,  but when they do it is devastating for all the Clans and most of the  time results in death. They live in Nests (houses) and sometimes they  have cats of their own as pets (Kittypets). Kittypets are fat, pampered  creatures that Clan cats disgust. A cat from a Clan must reject a  kittypet's soft life.
Sometimes there are even cats who aren't owned  by Twolegs or in a Clan called rogues. They are normally very selfish  and aggressive.  And lastly, there are also loners. A loner lives in  peace and doesn't defend its territory.
Below in a list I have posted the enemies the cats have had to fight in the past:
Twolegs  and Twoleg Monsters: Twolegs can capture cats in traps and their  monsters can eat trees and kill cats! They are greatly feared by even  the bravest warriors!
Badgers: Are big, lumbering animals with black  pelts, white stripes and tiny black eyes. They are capable of snapping a  cat with their paws, and their jaws are very powerful, able to crush a  cat's spine in one bite.
Other Cats: Cats are dangerous toward each  other and are mostly evenly matched. The only difference is that they  may differ in strength and other attributes.
Foxes: Are dangerous  because they normally hunt in mating pairs or small groups. They will  not hesitate to break into a nursery and take the kits.
Rats: Are  dangerous because they have advantage in numbers and can easily  overwhelm and eat a group of cats in only a few minutes. More organized  specimens have been known to work together as a team, and even speak cat  tongue.
Owls and Other Predatory Birds: Are dangerous because they  can sneak up, snatch up a kit in their talons and fly away, leaving the  Clan in shock and horror.
Sicknesses: Are dangerous because they can easily take the lives of elders and small kits. Plus, sickness travels quickly.
Anyway, that's all for now, I still have more information on warriors, but I will post this later.
See you!
- Spottedshadow