The Sun Java Lesson on Introspection defines Introspection as:
Introspection is the automatic process of analyzing a bean's design patterns to reveal the bean's properties, events, and methods. This process controls the publishing and discovery of bean operations and properties.ACTF, of course, can be used to introspect Javabeans but is primarily used to introspect Java rich-client GUIs. ACTF's introspection capabilities provide real-time views of the properties of GUI components that are relevant to assistive technologies such as screen-readers.
The following definition of Reflection comes from "Java Reflection in Action" by Ira R. Forman and Nate Forman:
Reflection is the ability of a running program to examine itself and its software environment, and to change what it does depending on what it finds.
To perform this self-examination, a program needs to have a representation of itself. This information we call metadata. In an object-oriented world, metadata is organized into objects, called metaobjects. The runtime self-examination of the metaobjects is called introspection.
ACTF uses the Java Reflection API to find information about your programs, like the constructors and methods invoked by the classes that comprise your application. This is what allows it to work on actual instances of objects (such as GUI components) in the JVM rather than source code for the classes of these instances.