Demonstrative is a pretty dramatic term to encompass a few simple (and familiar) words: THIS, THAT, THESE, THOSE.

Simplicity aside, we're going to embrace the word demonstrative so we can make far-fetched segues to discussing and drawing monsters. DeMONSTERatives. Yep.

THIS, THAT, THESE, and THOSE are like hand gestures specifying a spacial reference.

THIS thing here. THAT thing there. THESE dogs sitting on my knee. THOSE dogs salivating beside Pavlov.

They identify concrete objects or people.