Flash
From OLSEncyclopedia
Flash is a browser plugin that allows small (relatively speaking) applications to run within your web browser. This has a variety of uses, for instance, people often make movies or games in Flash, and annoyingly enough, entire websites.
Streaming video websites like YouTube and Google Video use Flash for their media player. The video itself is in a special format with the extension .flv, and while they can't normally be downloaded, they can be ganked using sites like KeepVid or Firefox extensions such as DownloadHelper. Don't let them fool you into installing a special player that just plays .flv files, as recent versions of VLC Media Player will play the format along with virtually everything else, with no need to install codecs or anything other than the player itself.
Flash uses a vector format for storing graphics, as opposed to a raster format, like most image and video formats. Vectors only have defined endpoints and properties, this means that they can be scaled to a larger or smaller size and retain the same visual clarity.
When Adobe bought Macromedia, they pretty much immediately updated the Flash plugin, including a brand new Flash 9 plugin for Linux users, who had been previously stuck on Flash 7 and had to resort to various open source alternative flash interpreters to run newer flash objects. They also fixed a number of issues, such as Flash 7 on Linux not displaying text inside text fields. This made flash games 100% more playable on Linux, as now you can see your objectives, the "how to play" screens, your score, etc.
Media Player Classic can play Flash files directly, which makes watching flash movies or playing flash games in full screen a lot easier.
For users of Firefox, installing Flash is even simpler than the process described on the installer download page, and doesn't require restarting the browser to work. Simply view a page that uses Flash without Flash installed, and Firefox will tell you that additional plugins are needed to view the page and give you the option to download and install the Flash plugin right then and there.
