From Stackoverflow by Kameshi Jungi
For understanding more about magento block types following are some built-in block types which are widely used in layout.
core/template: This block renders a template defined by its
templateattribute. The majority of blocks defined in the layout are of type or subtype of
page/html: This is a subtype of
core/templateand defines the root block. All other blocks are child blocks of this block.
page/html_header: Defines the header part of the page which contains the site logo, top links, etc.
page/template_links: This block is used to create a list of links. Links visible in the footer and header area use this block type.
core/text_list: Some blocks like
rightetc. are of type
core/text_list. When these blocks are rendered, all their child blocks are rendered automatically without the need to call the
page/html_wrapper: This block is used to create a wrapper block which renders its child blocks inside an HTML tag set by the action
setHtmlTagName. The default tag is
<div>if no element is set.
page/html_breadcrumbs: This block defines breadcrumbs on the page.
page/html_footer: Defines footer area of page which contains footer links, copyright message etc.
core/messages: This block renders error/success/notice messages.
page/switch: This block can be used for the language or store switcher.