GREP is a command line text search utility originally written for Unix, it stands for global regular expression parsing. Essentially, GREP in InDesign allows you to use codes to find and edit or style text through the Find/Change dialog box or Paragraph Styles. GREP is complex and can be intimidating, but it's not terribly difficult to learn the basics, and InDesign offers tools to make using GREP easy. Because of the depth of the subject, I'm only going to address GREP styles in this article.
