This page lets you set up two fragments of HTML which will get pre-loaded into the text editor box any time you're in a position to post a new node (for example, at the bottom of the Seekers of Perl Wisdom page).
You can use the upper part for whatever you want to pre-load in your posts. It is typically used as a template for your posts.
The lower part is treated as a .sig block by PerlMonks. It gets automatically wrapped with special HTML to make it "look like" a signature when people view your nodes.
For more details, see Signatures and Node Templates.
Both parts are optional and may be left blank.