The “1 Column” layout can be used to create a dramatic home page with a large image or focal point. It’s also a good choice for a landing page, or any other page that has a combination of text, images, and video.
The “2 Columns with Left Bar” layout is often used for pages with navigation on the left, such as a catalog or search results pages with layered navigation. It is also an excellent choice for home pages that need additional navigation or blocks of supporting content on the left.
With a “2 Columns with Right Bar” layout, the main content area is large enough for an eye-catching image or banner. This layout is also often used for Product pages that have blocks of supporting content on the right.
The “Empty” layout can be used to define custom page layouts. To learn more, see the Magento Design Guide.