“Real numbers are used to describe things that can be measured on a number line, like length or width. They can also be used for things like temperature, which can be negative or positive.
Complex numbers are used to describe things that have two parts, like a vector. They can be used for things like electric fields, which have a direction as well as a strength.
Quaternions are used to describe things that have four parts, like a rotation. They can be used for things like describing the orientation of a spacecraft.
Octonions are used to describe things that have eight parts, like a color. They can be used for things like describing the spectrum of light.”