flash
This tag refers to games and animations created for the Flash web platform using Shockwave/Macromedia/Adobe Flash (today, Adobe Animate).
While the Flash platform enjoyed success from the late 1990s to the late 2000s (especially because of the failure of the Java platform in the web), it eventually declined as JavaScript matured and more secure, more browser-independant platforms like HTML5 and WebGL made their entry and matured at their turn along with the reduced support for browser plugins.
Also worth noting is that something major happened to the Flash platform after version 9 (detailed in topic #15331), and it will have broken quite a few files that were made before the year 2011, so if you're looking at one of the older posts with this tag waiting for it to load, try viewing it in version 9's stand-alone player instead. Also, if you encounter such posts, ensure that it has the flash_9 tag.
Adobe has officially announced that browser support for Flash will be ceased by 2020.