Reiatsu

Reiatsu (Spiritual Pressure) is the physical force/pressure that a person’s creates when released. Most Shinigami, Arrancar, and quincy's can manipulate the release of their Reiatsu.

Reiatsu Sensing
The senses by which one feels and pick up on Reiatsu. Every person that has Reiatsu subconsciously uses both their sense of vision and their Reikaku at the same time in order to see.

Shape
Certain individuals can generate a shape or manifestation of their spiritual energy whenever they release enough of it; the manifestations are one of their inner strength.

Standard type
This is the most common form of Reiatsu, which has no effects other than those described above, along with its unique color and feeling. Most Hollows and Shinigami have this type, while Quincy and Humans always have this type. Notably, Fullbringers are Humans who have Hollow-like powers,

Dual type
All Visored and Arrancar have this specific Reiatsu; Visored feel more like Shinigami, while Arrancar feel more like Hollows. The Visored also feel more like Hollows when they release their powers. Arrancar seal their Hollow abilities and become as close to their original form as can be when they enter their Resurrección, explaining this phenomenon.

Element type
Two Shinigami have used elemental Reiatsu, even without releasing their Zanpakutō, with it being their natural power:

Fire & Heat

Ice & Cold