To parse means to break something down into units that can be analyzed. To parse a sentence means to break it down into its parts of speech. In computer terms, a compiler must parse source code so that it can be analyzed and then assembled into object code. An XML parser, for example, is a tool for reading eXtensible markup language documents. XML parsers can pass data to a browser if that data is "well-formed." XML doesn't provide an application programming interface (API) to an application, it just passes data to it. Both Microsoft and Netscape include XML parsers in their browsers.