This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
The method returns the path to a file, given the end part of it. This is probably best illustrated with an example: Imagine a web server (or web application) serving files from c:\files\fred which has a servlet published as "showme" designed to show a Java source file with syntax coloring. A request comes in to the server for the URL /servlets/showme?file=projects/source/Example.java Rather than hard code the "c:\files\fred" into the servlet (which would be very un-portable) the servlet can call String path = context.getRealPath(req.getParameter("file")); which should return: c:\files\fred\projects\source\Example.java ready for opening with a FileReader, or whatever.