Demonstrative pronouns are pronouns that have a strong “pointing” component. So instead of just standing in for an entity, they point a virtual index finger at it.
Many languages distinguish between two types – pointing here and pointing “over there”.
The most common English examples are “this” and “that”.
German has “dies-” and “jen-” but it also a third “generic” type that looks like the articles. So instead of saying “this”, Germans say “the”.