QuarkXPress ("Quark") is a computer application for creating and editing complex page layouts in a WYSIWYG environment. It runs on Mac OS X and Windows. It was first released by Quark, Inc. in 1987 and is still owned and published by them. The most recent version is 7.3.1 and includes editions for publishing in American English, International English, and over a dozen other languages.
QuarkXPress is primarily used by large publishing houses to produce the kinds of complex page layouts required by magazines, newspapers, catalogs, and similar printed materials. It is one of two products (the other being Adobe InDesign) that dominate that market space.