In a word-processing document, a 1-inch margin is the length between the edge of a page and the start of written copy. In Microsoft Word, 1-inch margins are standard for the top and bottom of a page, and 1 or 1 1/2-inch margins are standard for the sides.
Word normally has default settings for its standard margins, but people can change the margins to suit their preferences if 1-inch margins aren't desired. Smaller margins allow for more content on one page, but it may appear crammed. A 1-inch margin creates a boundary while allowing for more ample content than a larger margin.