Kompare is a free software graphical computer application which helps the user to compare two different text files or two directories. It is part of the KDE SC desktop environment and therefore primarily used on Linux and other Unix-like operating systems. Kompare does not actually compute the differences between the compared files itself, but is merely a graphical front end to the command line interface diff utility.
It is a standard KDE SC tool, it comes packaged with the kdesdk module.
Kompare was previously known as "kdiff".
Read more about Kompare: Comparing Text Files, Other Features of Kompare