Application program and applet program.

An applet is client side program which is downloaded in client side and run in the browser. Applet program can not access network connection like opening socket ,writing to socket. A class extending java.awt.Applet class which has methods like init(), start(), stop(), destroy(),paint() overridden. And cannnot write to client side files i.e. hard disk.
An application runs standalone with a support of virtual machine. An application does not have nay restrictions as Applets have over network and file related activities.They are free to open sockets over a network read and write to a file.