Demi-Hollow: Is a human spirit slowly turning into a Hollow.
Although this phase usually takes up to a month, unless it’s
forced by opening the hole a hole in the spirits chest.
The Death Gods perform the soul burials so that the spirit won’t
be turning into a Hollow.

Earthbound spirits: These are human ghosts wandering an area
that was important to them during their lifetime.

Hollows: These are the evil spirits, that the Death Gods fight.
There are different ways of turning into a Hollow: You will turn into
a Hollow when your Chain of fate is destroyed. Another way is when
the hole that spirits have in the chest is forcefully opened. And you
can also turn simply by being eaten by a Hollow.

Menos: Is a gigantic Hollow made from an enormous amount of
Hollows combining into one.

Modified Souls: Are artificial spirits made to be inserted into a dead
human body, giving it the power to fight Hollows. The mod-souls
have enormous power that are way over human limits.

Pluses: These are the kind souls. They are not harmful to anyone,
and are sent to Soul Society by the Death Gods through soul burial
- where they can finally rest.