Eywa is the deity to the Na'vi as well serving as a colloquially to Na'vi religion. The Na'vi believe that Eywa acts to keep the ecosystem of Pandora in perfect equilibrium. It was theorized by Dr. Grace Augustine and others that all living things on Pandora connected to Eywa through a system of neuro-conductive antennae; this often explains why Na'vi can mount their direhorse or mountain banshee steeds and ride them immediately without going through the necessary steps required to domesticate such wild animals.
Mythology & Origins.Edit
Humans do not know when or how the Na'vi came to the conclusion of creating a deity, but some theorized as to why humanity have created religions; to explain events or to create a society under a unifying banner. However, the Na'vi all believe in Eywa with no one clan having a difference of opinion about Eywa. Dr. Grace Augustine also came to the conclusion that Eywa was partially formulated on the basis of something keeping a balance on Pandora to which no scientist have come to the conclusion as to why.
Upon the suggestion of the Na'vi song surrounding the Star Tree, it is believed that Eywa came to fruition from the Star Tree itself, an all beautiful (feminine) and a balanced tree that provided shelter for both clans that fought fiercely over. Despite what is known of the origins surrounding Eywa, it is known that Eywa is the common explanation for many things that do happen on Pandora.
Some believe that this interconnectedness, which on Earth is merely a spiritual concept, exists in a physical and tangible way on Pandora, in the form of a strange, collective psionic consciousness embedded in the planet, drawn from all Pandoran life. It is, in a way, a little like a huge biological internet; the trees being computer servers that store information. The Na'vi can upload or download memories from it using their queues and it can even be used for mind transfers in certain cases.
The Tree of Souls grants the Na'vi access to the psychic essences of their deceased, which is how the Na'vi communicate with their ancestors. The roots of the trees are capable of extending above the ground and connecting to the nervous system of any living thing, even humans. This is how Jake Sully's consciousness was transferred to his avatar permanently.
Pandora as Eywa.Edit
A few human scientists have concluded that Pandora could possibly be alive in that, Pandora's neural network has allowed to create a sentient creature that recognized itself as being alive and with a functioning mind. But this idea has been met with heated debate amongst many other drivers who are involved day-to-day with the Na'vi.