Originally called Macromedia flash and now Adobe flash since Adobe acquired Macromedia, it is a multimedia platform for adding animation and interactivity to web pages. Since flash is not nativeally supported by browsers, a free plugin is needed and can be downloaded from Adobe systems. The fact that it requires a plugin could be considered a disadvantage, however, nearly all browsers these days have the flash plugin installed so it is not really a problem. Flash is commonly used to create animation, advertisements, and various web page components, to integrate video into web pages, and more recently, to develop rich Internet applications. Flash can manipulate vector and raster graphics and supports bi-directional streaming of audio and video. It contains a scripting language called ActionScript
Files in the SWF format, traditionally called "ShockWave Flash" movies, "Flash movies" or "Flash games", usually have a .swf file extension and may be an object of a web page, strictly "played" in a standalone Flash Player, or incorporated into a Projector, a self-executing Flash movie (with the .exe extension in Microsoft Windows). Flash Video (FLV) files
Flash can be used to create entire websites thus nearly eliminating all HTML. We do not advise this even though some visually pleasing sites are created this way. One of the reasons is that it is not SEO friendly, search engines generally ignore it as they do images without an accompaning ALT tag. Also it can lead to some long and annoying site intros leading to most users to click on the "skip intro" link. This site uses flash as a component but is not a flash site. In addition this site also has an html version which is seen by search engines and can be selected by the user. The intro is played only for the first visit to the home page and then skipped for subsequent visits to the home page. Another reason for not having a pure flash site is that the site is more difficult to maintain and adapt and does lend itself to DHTML and other interactive techniques.