What is the SWT? The Standard Widget Toolkit was created by IBM, and it was intended as a replacement for both the Java Abstract Windowing Toolkit (AWT) and Swing.
The SWT is an extensive GUI toolkit, as you'd expect if it was intended to replace both the AWT and Java Swing. Controls are called "widgets" in the SWT. Here's the current list of the available SWT widgets:
As you can see, the SWT is a serious GUI toolkit.