Ranked in these QuestionsQuestion Ranking
Pro Command Line Interface makes it easy to use for people who work a lot in the terminal
Great for creating patch files, using with other *nix utilities (for example, colordiff). Does not require a GUI.
Pro Creates patches
These patches can be used to apply the differences to the same source file at a different storage location (different folder, different machine).
Pro Multiple formats
The difference can be output in formats known as normal, unified, ed, rcs, and side-by-side.
Pro Compares entiry directory trees
Two directory trees can be compared file by file recursively. All differences are output concisely.