What does positive and negative connotation mean?

Positive and negative connotations denote how a word or phrase is used positively or negatively in society.

Denotation is the dictionary definition of a word. For example, according to Dictionary.com, the word cool means "moderately cold; neither warm nor cold"; however, common usage of the word means something good or awesome or interesting (positive connotation). Any dictionary tells us that the word pig means a barnyard mammal; however, in some regions, the word is used to refer to police officers in a negative way (VERY negative connotation).