Letter head is the heading at the top of a sheet of letter paper (stationery).
That heading usually consists of a name and an address, and a logo or corporate design, and sometimes a background pattern. The term “letter head” is often used to refer to the whole sheet imprinted with such a heading.
Many companies and individuals prefer to create a letterhead template in a word processor or other software application. This generally includes the same information as pre-printed stationery, but at lower cost. Letterhead can then be printed on stationery (or plain paper) as needed on a local output device or sent electronically.
Letterheads are generally printed by either the offset or letterpress methods. In most countries outside North America, company letterheads are printed A4 in size (210 mm x 297 mm).  In North America, the letterhead size is typically 8.5 x 11 inches.