Block Types in Magento

Magento uses some mostly commomn built-in blocks which are as follows.
core/template: It will renders a template defined by its template attribute. The majority of blocks defined in the layout are of type or subtype of core/template.
page/html: It's a subtype of core/template and defines the root block. All other blocks are child blocks of this block.
page/html_head: It will help the HTML head section of the page which contains elements for including JavaScript, CSS etc.
page/html_header: It will help the header part of the page which contains the site logo, top links, etc.
page/template_links: It is used to create a list of links. Links visible in the footer and header area use this block type.
core/text_list: This will allow Some blocks like content, left, right etc. are of type core/text_list. When these blocks are rendered, all their child blocks are rendered automatically without the need to call the getChildHtml() method.
page/html_wrapper: It 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: It will help to define breadcrumbs on the page.
page/html_footer: It will help to define footer area of page which contains footer links, copyright message and other static links
core/messages: It will help to renders error/success/notice messages.
page/switch: It will help to used for the language or store switcher.

Note:There are many more but this are commonly used