The KDiff3 Handbook

compares and merges two or three text input files or folders,

shows the differences line by line and character by character(!),

provides an automatic merge-facility,

has an editor for comfortable solving of merge-conflicts,

provides network transparency via KIO,

has options to highlight or hide changes in white-space or comments,

supports Unicode, UTF-8 and other file encodings,

prints differences,

supports version control keyword and history merging.