Total Words :
Unique words are uncommon words that reflects your site features and informations. Search engine metrics are not intended to use unique words as ranking factor but it is still useful to get a proper picture of your site contents. Using positive unique words like complete, perfect, shiny, is a good idea user experience.
Stop words are common words like all the preposition, some generic words like download, click me, offer, win etc. since most used keyword may be a slight factor for visitors you are encouraged to use more unique words and less stop words.