Layout Components were created to make developing and managing site layouts easy. Namely, they should solve these goals (from a 2005 CFDJ article):
The following goals should also have been included:
Layout Components have been enhanced slightly in the years since that article, but remain fundamentally the same today (this is being written in early 2010).
Here is a sample page using Layout Components (with the optional cf_Template tag):
<cf_Template title="Page Title">
(some content here)
</cf_Template>
The rest of the documentation should make clear how Layout Components meet all of the goals above.