Dr. Grace Augustine is a xenobotanist in charge of the Avatar Program, who arrived several years before the avatar team. She explored Pandora, a moon of the planet Polyphemus, and literally wrote the book on its plant life and biology. She was the only person who was able to catalog all the species and discovered the "organic computer" of Pandora's ecosystem that defeated the invading American exploiters and destroyers of the Navi's home tree in their ruthless quest for unobtainium- one of the most powrful sources of energy in the universe. As an astrobiologist, Grace learned that all living things on Pandora connect to Eywa through a system of neuro-conductive antennae.
To Grace, this interconnectedness, which on Earth is merely a spiritual concept, exists as a physical biologoical network, in the form of a mysterious, collective psionic consciousness embedded in the planet, drawn from all Pandoran life -a massive bio internet with the trees computer servers that store and relay information. The Na'vi can upload or download memories from it using their qeueus and it can even be used for mind transfers in certain cases.
At her death, Grace's consciousness did not successfully transfer to her avatar, the neural link created when the tendrils of the Tree of Souls interfaced with her human body allowed her full memories to be "downloaded" into the "organic computer" of Pandora's ecosystem. Later, Jake begged Eywa for help in the struggle against the Avatar RDA Scorpion Gunship by asking it to access Grace's memories, which would reveal how Earth's ecosystem had been destroyed by humans, a danger which Pandora now faced. Eywa heard Jake's plea and summoned the life forms of Pandora to his aid.