What is the difference between the different demonstrative pronouns?

First of all, we need to define what a demonstrative pronoun is. A demonstrative pronoun takes the place of a noun in a sentence. When discussing demonstrative pronouns in Spanish, proximity (how close we are to the object) is the most important factor. In Spanish we have 3 categories, each one differing in our proximity to the object and each having masculine, feminine and plural forms of the pronoun. Category one = this/these, category two = that/those and category three = that/those over there. 

The first category is used when replacing a noun that is very close to the speaker. The pronouns list as follows: éste (masculine singular), ésta (feminine singular), éstos (masculine plural), éstas (feminine plural). E.g. Yo quiero ésta aquí. The second category is used when replacing a noun that is not very close to the speaker. These pronouns are as follows: ése (masculine singular), ésa (feminine singular), ésos (masculine plural), ésas (feminine plural). E.g. Ésas son las más bonitas. Lastly, the third category is used when replacing a noun that is far from the speaker. These pronouns are as follows: aquél (masculine singular), aquélla (feminine singular), aquéllos (masculine plural), aquéllas (feminine plural). E.g. Aquéllos son los jefes. Also, note that there are three neuter demonstrative pronouns, one for each category: esto (this), eso (that) and aquello (that one). These are used to refer to unknown concepts and things.