Named scopes are a really powerful feature of models - they allow you to define a clean, concise syntax when performing queries within your models - and best of all, are really easy to utilize in CodeIgniter. The main principle of a named scope is that you create a method that, combined with method chaining, allows you to add details to your query (generally additional WHERE clauses).

He shows two "before and after" examples of multi-line requests condensed down by making a custom model layer with methods containing the commonly used portions of the database calls and returning the "$this" object so it can be used for chaining.