The three realms—the Triloka—are that of desire, that of form, and
that of formlessness.
There in the realm of desire, forms of desire for sex and food
predominate, and all living beings dwell everywhere from the six
heavens of desire, to the four inhabited continents of each universe
where we are, and down to the hells; there in the realm of form, all
living beings with outward appearance dwell in the four dhyana heavens
or eighteen Brahma heavens; and there in the realm of formlessness,
all living beings with mind and cognition anchoring in the ability to
overcome all disturbing thoughts dwell in the four immaterial heavens,
namely, the states of boundless space, of boundless knowledge, of
nonexistence, and of neither thinking nor not thinking. The three
realms, conclusively, are where ordinary human beings journey between
rebirths and redeaths. Practitioners emulating the Buddha need to
focus on liberating themselves from transmigration and strive hard in
pure progress.
The six ways of sentient existence are the three virtuous paths and
three evil paths of transmigration combined. The three virtuous paths
pertain to the heavens, human realm, and azura state, and the three
evil paths to the hells, hungry ghosts, and animals. The six ways of
sentient existence denote the process in which all living beings therein
generate a certain cause to duly beget a certain result and hence
proceed from cause to effect. The six ways of sentient existence are
also known as six destinies.