leftcolumn
This page does not have right column. It only has left column and content part.
You can disable any content section for a specific page via Visual Mode.
Custom Block
This custom block is created in Admin Dashboard. You don't need to edit any html / php files to create new blocks. Everything could be easily created in admin panel.
You can create several types of blocks including Smarty, HTML, Plain Text or even PHP. Check Admin Dashboard / Content / Blocks management page.