Intension refers to the meanings or characteristics encompassed by a given word. It can be understood as a word's connotation. Intension is often discussed with regard to extension. Extension refers to the class of things to which the word can be applied. In a simpler sense, the intension of a word can be thought of as the collections of associations the word creates in the mind of someone using or hearing it, while extension (or denotation) refers directly to the referent or referents that the word describes.
We can conceptualize the creation of words as a leap from the object or idea the word is intended to describe to the word itself, with the creation of meaning as an intervening variable. If this is the case, then intension lies between the object and the word as a part of the creation of meaning, and extension lies on the side of the object being described.