Software applications for deleting, uninstalling or removing, computer files.
File comparison, synchronization, and merge utilities, from the humble Unix "cmp" and "diff" to more visual and interactive utilities. These show how two files, especially text files, are different, and often what needs to be changed to make them identical - which lines need to be inserted, deleted, changed, or moved. This helps to join two versions of a document, or to see what changed between versions.
Comprehensive software for organizing files, viewing files, browsing through directories, moving files, renaming files, deleting or recovery of files, often searching, compressing/decompressing, or other features. The sort of thing the Windows Explorer or File Manager, or Macintosh Finder program does.
Programs that will search multiple files for specific content, and return a list of those files that contain it. These will usually search text files, for specific text. Some will even replace some text with other text across several files. Many operating systems include a version of these tools built in, such as the Windows Find: All Files, or the Macintosh Finder. The classic Unix command line utility for this is called grep, an abbreviation for "global regular expression print".