Java Swing is a technology for creating Graphical User Interfaces (GUIs) for Java applications.  Swing provides the ability to have a pluggable look and feel applied to applications providing a consistent unique design across applications.

Swing is the successor to the Abstract Window Type (AWT) class provide by Java to create GUIs, although it doesn't replace all the functions of the AWT.  Swing is to be used for the presentation of Java programs.