A diagram displaying equal margins of width 25mm on an A4 page.
In typography, a margin is the area between the main content of a page and the page edges. The margin helps to define where a line of text begins and ends. When a page is justified the text is spread out to be flush with the left and right margins. When two pages of content are combined next to each other (known as a two-page spread), the space between the two pages is known as the gutter. (Any space between columns of text is a gutter.) The top and bottom margins of a page are also called "head" and "foot", respectively.
The default margins for Microsoft Word from version 2007 onward have been 1 inch (2.54 cm) all around; in Word 2003, the default top and bottom margins were 1 inch (2.54 cm), but 1.25 inches (3.17 cm) were given at the left and the right.OpenOffice Writer has 0.79 inch (2 cm) all around.LaTeX varies the width of its margins depending on the font size. By default, LaTeX uses 1.5 inches margin sizes for 12pt documents, 1.75 inches for 11pt, and 1.875 inches for 10pt—relatively large margins. These adjustments are intended to allow a maximum of 66 characters per line, to increase readability. However, studies have shown that longer line lengths (more than 66 characters per line) can improve readability 
The term "margin" can also be used to describe the edge of internal content, such as the right or left edge of a column of text.