The broadsheet is a size of paper and a type of newspaper.
Broadsheet as a Paper SizeIn printing a broadsheet is a sheet of paper that is typically between 14 to 18 inches wide and 22 to 25 inches tall. This may also be called a half broadsheet because the publication (usually newspapers) are typically printed on paper that is twice the size of a broadsheet then folded in half, creating 4 pages of the publication. See the wide range of broadsheet paper sizes used in the US and other countries.
In addition to newspapers, a broadsheet also refers to any type of large flier or advertisement. These advertisements are often printed on half or full broadsheet papers and inserted into newspapers.
A broadsheet size publication is one with a finished size (no matter what size of paper is used) of a broadsheet — with the actual size varying by country and even by individual publication. The more or less standard 17 x 22 inch US broadsheet can be cut into various half sizes to create other standard publication sizes. Half of a broadsheet is tabloid size. A quarter of a broadsheet is letter size. An eighth of a broadsheet is digest or booklet size.
Broadsheet as a Type of JournalismAt one point in time serious or professional journalism was found predominantly in broadsheet size newspapers. Tabloid size newspapers, on the other hand, were typically less serious and often sensationalist, covering much more celebrity news and alternative or fringe news topics. Tabloid journalism became a derogatory term. Today many so-called serious publications are downsizing to tabloid size (also referred to as compact) papers.
"And while broadsheet readers tend to be upscale suburbanites, tabloid readers are often working class residents of big cities. Indeed, many city dwellers prefer tabloids because they are easy to carry and read on the subway or bus. ...But there's an important distinction to be made here. True, there are the over-the-top tabloids like the Enquirer, but there are also the so-called respectable tabloids - such as the New York Daily News, the Chicago Sun-Times, the Boston Herald and so on - that do serious, hard-hitting journalism. What's the Difference Between Broadsheet Newspapers and Tabloids? | About.com Journalism
Also see: What is Tabloid?