The preloaded text is from Robin Hood by Howard Pyle. You can start searching it now. You can load all of Robin Hood (included in the download) or any plain text file, but the part of speech sorting will work only if the POS is included in the text file, immediately follows the word, separated by /.
Click on a column heading to sort it, or reverse its sort. Mouse over an item for its part of speech, or click on it to get information about the distribution of its parts of speech, if they are present. Alt-click on a hit to see it in a larger context.