Kashyyyk is a world enveloped in immense forests. Inland, the trees are so tall and dense that a layered ecoystem has evolved within its branches. The closer one approaches to the forest floor, the more dangerous and primeval the environment becomes. Wookiees inhabit the upper levels of the forest, having built their massive cities within the interwoven canopy.
Though Wookiees do have a primitive appearance, they are quite comfortable with advanced technology. They can repair and maintain modern starships. They have developed a unique projectile weapon called a bowcaster. The Wookiee city of Thikkiiana was one of the key manufacturers of sophisticated computer componentry in the New Republic.
An average adult Wookiee stands more than two meters tall, and has a lifespan of several centuries. Aside from great strength and keen senses, Wookiees also have impressive regenerative abilities that allow them to recover from injury at a remarkable rate. Wookiees also have wickedly curved retractable claws used for climbing. Wookiee honor dictates that these claws are never used in fighting. A Wookiee that breaks this covenant is shunned and exiled, branded a "madclaw" and banished from the cities.
Wookiees are deeply respectful of nature, and have a strong connection to the sanctity of their world's ecology. When the Empire began exploiting the Wookiee homeworld, it was as if the giant people felt the pain inflicted upon Kashyyyk. Wookiees have also shown their own particular affinity for the Force.
When the Empire legalized slavery, one of the first species to profit were the Trandoshans. These reptilians are from a world neighboring Kashyyyk, and have long had grievances with the Wookiees.
Though Wookiees can understand Basic, and other galactic languages, their limited vocal apparatus can only produce their native tongues. The most common Wookiee language is Shyriiwook, a dialect of barks, growls, howls and roars. Wookiee language is very complex and liquid. Violence is such an everyday concern that there are 15 separate words for it in the Wookiee vocabulary. Wood and the crafting of woodwork and technology is so important that over 100 words exist to describe it.
Wookiees have a primitive patriarchy with a complicated lineage structure, initiation rites, and a religion that rejects materialism. One of the most important Wookiee customs is Life Day, wherein extended Wookiee families gather and celebrate a day of joy and harmony, as promised by the Tree of Life. Even the Imperial blockade could not keep Wookiees from recognizing this most important day.
Wookiees greatly value morality, courage, compassion and loyalty. A sacred and ancient Wookiee tradition is that of the honor family. An honor family comprises a Wookiee's closest friends and companions. These family members pledge a commitment to lay down their lives for one another, as well as members of any honor families these individuals may have. Like the similarly sacred Wookiee life debt, Wookiees extend this tradition to members outside their species. Chewbacca considered Han Solo, Leia Organa Solo, their children and Luke Skywalker part of his honor family.
After the Empire was overthrown, the Imperial slaving operation collapsed. The invading Nagai aliens attempted to resurrect the despicable practice, but were repulsed by agents from the Alliance of Free Planets. Nothing related.