Wakan means sacred, or possessed of power that is not ordinary. Wakan Tanka is usually translated Great Spirit, which pulls it toward a single creator god, or Great Mystery, which is closer. In older Lakota usage it functions as a collective: the sum of the sacred powers, sixteen of them in the accounts recorded from Oglala holy men, grouped in fours, including Wi the sun, Skan the sky or motion, Maka the earth and Inyan the rock. Whether this is a pantheon, an aspectual unity, or a system tidied up by its recorders is a genuine scholarly argument, sharpened by the fact that Christian influence had been present for generations before anyone wrote it down.
The canupa, the sacred pipe, is the central object. Lakota tradition holds that it was brought by White Buffalo Calf Woman, who appeared to two scouts, instructed the people in its use and in the rites, and departed as a buffalo calf. The bundle she is said to have left is kept by a hereditary keeper of the Sicangu Lakota and has not been made a public object. Smoking a pipe binds what is said over it; the smoke carries words, and a pipe is opened to seal an agreement, to begin a ceremony, and to make a request.
Mitakuye oyasin, all my relations, closes prayers. It is a kinship statement, not a sentiment: it asserts that the speaker stands in obligation to animals, to the dead, to the powers and to the ground, in the same idiom used for cousins. Lakota kinship terminology is elaborate and the religious vocabulary borrows it wholesale.
A wicasa wakan or holy man is not a priest of a congregation. Authority comes from vision, from apprenticeship to another holy man, and from results, and it is not conferred by any institution. There is no Lakota church, no orthodoxy and no central authority to settle disputes, which is why practice varies between communities and between families.