A common element in conventional documents is the block quote, a lengthy copy of text from another document. Traditionally, short quotes are set off with quotation marks, while block quotes are made entirely of separate paragraphs within the main document, typically with special indentation and sometimes italicized.
All of the text within the <blockquote> and </blockquote> tags is set off from the regular document text, usually with slightly more-indented left and right margins, and sometimes in italicized typeface. Actual rendering varies from browser to browser, of course.
The HTML standard allows any and all markup within the <blockquote>, although some physical and content-based styles may conflict with the font used by the browser for the block quote. Experimentation will reveal those little warts.
The <blockquote> tag is often used to set off long quotations from other sources:
We acted incorrectly in arbitrarily changing the Kumquat Festival date. Quoting from the Kumquat Growers' Bylaws: <blockquote> The date of the Kumquat Festival may only be changed by a two-thirds vote of the General Membership, provided that a <strong>60 percent quorom</strong> of the Membership is present. </blockquote> (Emphasis mine) Since such a quorom was not present, the vote is invalid.