Adobe Flash is officially near the end of its life cycle, and will see support end after 2020. Until the end of that year, Adobe will continue to issue security patches, and ensure Flash is compatible with major OSes, browsers, and other agents that require compatibility for one reason or another. After the end of 2020, Adobe will stop offering support for Flash, will no longer distribute it, and will begin encouraging content producers to move away from it and port existing Flash content over to other standards. Adobe also announced in its press release on the matter that it intends to "move more aggressively" toward shutting Flash down in some territories due to the use and distribution of unauthorized versions of Flash that could be outdated, insecure, or compromised.
According to Adobe, web plugins like Flash and its ilk pioneered many of the standards and types of media that are seen on the internet these days. Recently, however, those functionalities have been supplanted and even improved upon by more open standards that are easier to use, easier on computer systems, and arguably more secure. HTML5 is one such example; the standard was considered the underdog to Flash for quite some time, but once it proved its worth and got a wider number of content producers on board, it managed to handily replace most uses of Flash, aside from legacy content that webmasters and developers had yet to port over.
Adobe Flash was disabled on Android back in 2012, though unofficial means do exist to get the plugin up and running in one of the few supporting browsers left in the Android ecosystem. Unofficial or not, Flash on Android has historically been lambasted as an incomplete and subpar experience compared to using it on a PC, where it has often been criticized over security vulnerabilities and heavy resource usage. Likewise, Google is on track to disable the use of Adobe Flash in its Chrome browser at the same time support from Adobe ends, and that will likely mean the end of support on Chrome OS, as well. The demise of Flash paves the way for standards like HTML5, WebGL, and WebVR to march into the mainstream.