Java Gene

• Java bytecode is what gives it the key part of its name. The bytecode is in Java, one of the most influential programming languages today. Most Java-enabled browsers can understand it. It is technology agnostic and as such it allows the Applet to run in the browser hosted on all major platforms like Windows, Mac, Unix and Linux.
  
  

Program

• Java Applet is in essence just a program. It is normally coded in Java but that doesn't always have to be the case. Languages that compile into Java bytecode like Jython, Ruby and Eiffel could also be used.
  
  

Special

• Any Java program can't qualify to be an Applet. The program class needs to be a subclass of the java.applet.Applet class for web usage or a subclass of javax.Swing.JApplet for stand-alone application usage. Similar restrictions will apply in other languages that compile into Java bytecode.
  
  

Embedded

• An Applet can be included in the Web page by the usage of applet or object HTML tags. The browser then downloads the Applet and embeds it in the Web page when the page is first accessed. The applet tag is now deprecated and hence not recommended. Although the usage is still quite common as it is the only tag that offers common support for all major browsers. As of early 2010, the object tag needs the support of JavaScript to make that happen and therefore its use is not as prevalent.
  
  

Sandbox

• The Web is not the safest of places and client resources need to be protected from unwarranted access. It is for this reason that the Applet can only operate in its own sandbox. Its access rights are limited. As an example it can't access the file system of the client computer or read from its clipboard.
  
  

Capability

• A Java Applet will add additional capability not otherwise possible in the available environment. As an example, it can be used to provide advanced interactive features that can be built around capturing mouse inputs. HTML and JavaScript are not potent enough to help there. It can also be used for computational intensive visualizations using 3-D hardware acceleration possible with Java.