Tsaheylu has several different uses to different creatures, but primarily, it allows two beings to mentally connect and share information with one another. This information can be verbal communication, such as when a Na'vi issues commands to a banshee or direhorse to direct it without the use of reins, memories, and even sensory data. When two creatures are bonded, they gain access to each other's physical senses; this means they will feel the pain of whatever they are bonded to, among other things. The slinger makes use of this ability greatly, as its head and body are two separate entities connected by their queues, and the body does not possess eyes, meaning cannot see when its head is disconnected and must navigate with sound.
Taming and riding creatures by use of tsaheylu is especially important to the Na'vi, wherein successfully bonding with and learning to ride direhorses, banshees, and other creatures is part of certain rites of passage into adulthood, including Iknimaya. The Na'vi also bond with each other when they mate to create a profound, lifelong spiritual bond with one another. It should be noted that tsaheylu is not considered erotic outside of the context of mating, nor is the queue part of a creature's genitalia.
Certain Pandoran florae can also perform tsaheylu with other creatures and plant life; this connection builds the foundations of the Pandoran neural network. This network can be accessed by the Na'vi and presumably other life forms at areas like the Tree of Souls and Tree of Voices; when a Na'vi connects with the network to commune with Eywa, they can upload their own memories and consciousness to the network, and even communicate directly with the spirits of the deceased.
- The correct spelling of this word was controversial. In all official written sources, it was spelled tsahaylu prior to the DVD/Blu-ray release. Due to the pronunciation that is constantly used in the Avatar film, the correct transcription should be tsaheylu, because the -ay- sound coincides with the sound found in English words like eye, whereas the -ey- sound is present in words like they. This was confirmed by the DVD subtitles, where the tsaheylu spelling is used. Furthermore, the inventor of the Na'vi language, Paul Frommer, mentioned tsaheyl si as an expression for to bond with in an interview.
- Before Paul Frommer was tasked with the development of a language for the Na'vi, James Cameron used shahaylu as the word for the bond as reflected by the script.