Ce, Ceci, Cela, Ça are "Indefinite Demonstrative Pronouns" whereas Ce, Cet, Cette, Ces are "Demonstrative Adjectives" One of them is an adjective and must be used with a noun. The other is pronoun. For example, Je ne veux pas ceci, je veux cela. (I don't want this, I want that) Cette idée est intéressante. (This idea is interesting) Note that ceci=ce + ici(here) and cela=ce+là(there)