The kdelibs package consists of the following libraries:
The kdecore library is the basic application framework for every KDE based program. It provides access to the configuration system, command line handling, icon loading and manipulation, some special kinds inter-process communication, file handling and various other utilities.
The kdeui library provides many widgets and standard dialogs which Qt doesn't have or which have more features than their Qt counterparts. It also includes several widgets which are subclassed from Qt ones and are better integrated with the KDE desktop by respecting user preferences.
The kparts library forms the foundation for KDE's embedded components model.
The kio contains facilities for asynchronous I/O and access to mimetype handling.
The kfile library contains the KDE file dialog and its helper classes.
The khtml library contains the KHTML part, a HTML browsing widget and parser, including interfaces to Java.
The kjs library provides an implementation of JavaScript.