They are instead based on term-definition pairs. When the above list is displayed , it arranges the elements such that each term is associated with the corresponding definition. The exact arrangement of elements may vary from browser to browser. Similar to ordered and unordered lists, definition lists can be arbitrarily long. You can leave out one part of a DT-DD pair, but it is not recommended.
Definition lists are perfect for creating glossaries.
For example, the Beginner's Web Glossary on this server is simply one relatively long definition list.