Nesting

Nesting is a term used in HTML and general programming to refer to the placement of listings within one another. By definition, lists with nesting contain sublists.

URLs:

A Beginner's Guide to HTML

Explains how nesting is used in HTML

W3E References:

HTML

markup

Detail:

This is an example of nesting:

1. first item
   1. first item of nested list
   2. second item of nested list
2. second item