Macromedia Flash (later Adobe Flash) was a multimedia web browser plug-in that enabled animations, video, and interactive content on websites. Flash was an extremely popular plug-in for more than a decade, but it eventually fell out of favor due to a combination of performance and security problems and the introduction of HTML5 and its multimedia features.
Originally called FutureSplash Animator and released in 1996, Flash first became popular as a vector-based animation tool. It allowed people to easily create animations that could be played back in any web browser with the Flash plug-in installed. Later updates introduced ActionScript (an object-oriented programming language that added new levels of interactivity) and support for high-quality video streaming. By 2010 the Flash plug-in was included by default with most web browsers, and it was common to see interactive games, streaming video, and even entire websites built using Flash.
However, the Flash plug-in had its drawbacks. It was very resource-intensive when content was playing, quickly draining batteries on laptop computers. The plug-in also proved to be a security risk that allowed an attack vector for malware. The lack of support for Flash on Apple's iPhone, and growing browser support for HTML5 video, ultimately caused Adobe to end support for the Flash plug-in in 2020. The animation tool itself was renamed Adobe Animate and now supports HTML5, WebGL, and SVG animation output.
NOTE: "Flash" may also refer to flash memory. Erasing a flash memory cell is often called "flashing" the memory.