Definition - What does JApplet mean?
JApplet is a java swing public class designed for developers usually written in Java. JApplet is generally in the form of Java bytecode that runs with the help of a Java virtual machine (JVM) or Applet viewer from Sun Microsystems. It was first introduced in 1995.
JApplet can also be written in other programming languages and can later be compiled to Java byte code.
Techopedia explains JApplet
Java applets can be executed on multiple platforms which include Microsoft Windows, UNIX, Mac OS and Linux. JApplet can also be run as an application, though this would require a little extra coding. The executable applet is made available on a domain from which it needs to be downloaded. The communication of the applet is restricted only to this particular domain.
JApplet extends the class in the form of java.applet.Applet. JApplets are executed in a tightly-controlled set of resources referred to as sandboxes. This prevents the JApplets from accessing local data like the clipboard or file system.
The first JApplet implementations were performed by downloading an applet class by class. Classes contain many small files and so applets were considered to be slow loading components. Since the introduction of the Java Archive (or simply JAR file), an applet is aggregated and sent as a single, but larger file.