An applet is a software component that runs in the context of another program, for example a web browser. An applet usually performs a very narrow function that has no independent use. Hence, it is an application -let. The term was introduced in AppleScript in 1993. An applet is distinguished from "subroutine" by several features. First, it executes only on the "client" platform environment of a system, as contrasted from "servlet." As such, an applet provides functionality or performance beyond the default capabilities of its container (the browser). Also, in contrast with a subroutine, certain capabilities are restricted by the container. An applet is written in a language that is different from the scripting or HTML language which invokes it. The applet is written in a compiled language, while the scripting language of the container is an interpreted language, hence the greater performance or functionality of the applet. Unlike a "subroutine," a complete web component can be implemented as an applet.
The word applet could alternatively be used to describe a small standalone application, such as those typically bundled with operating systems, for example a calculator program or text editor.

Interfaces
Unlike a program, an applet cannot run independently; an applet usually features display and graphics and often interacts with the human user. However, they are usually stateless and have restricted security privileges. The applet must run in a container, which is provided by a host program, through a plugin, or a variety of other applications including mobile devices that support the applet programming model.