QuarkXPress ("Quark") is a computer application for creating and editing complex page layouts in a WYSIWYG (What You See Is What You Get) 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.
QuarkXPress is used by individual designers and large publishing houses, primarily to produce any kind of layout, from flyers to complex page layouts required by magazines, newspapers, catalogs, and similar printed materials.
Along with Adobe InDesign, it dominates that market space.