is for the list object in Lisp programming. A list represents a sequence of zero or more elements. Emacs Lisp relies extensively on the list data structure; it is a fundamental building block. Emacs provides many facilities for building, modifying, extending, and efficiently handling list data structures.
Use separate tags for association-lists and property-lists.
Emacs provides additional functions for using lists as sets.
Emacs Lisp extends the basic list structure to more complex data-structures, such as sequences.