SWF (acronym of “Shockwave Flash”) actually is a Flash movie, and it can be viewed as a Flash animation format, while the FLV is Flash Video, Flash Video is the name of a file format used to deliver video over the Internet using Adobe Flash Player .
More specifically, SWF is a proprietary file format for multimedia and especially for vector graphics. It can contain animations or applets of varying degrees of interactivity and function in order to be small enough for publication on the Web. Therefore, SWF is currently the dominant format for displaying animated vector graphics on the web which is very popular and be commonly used. What’s more, SWF is sometimes used for creating animated display graphics and menus for DVD movies, and television commercials.
FLV, as a Flash video format, is also very popular on the web. You can always see the videos on the website like YouTube, Google Video, MySpace TV. After you download the video from YouTube, you will find the downloaded video’s file extension is .flv, which means it is the FLV video. It is also in a small size and can be loaded on the web easily. We can take the YouTube video as an example, the video on the website we can consider as a FLV files with a player in it. Once you download it to your local computer, you just download the content, that is the FLV, to your website, but the player is still on the YouTube website. If you want to play the FLV on your website, you need to embed it to a player. While the SWF can be seen as a container and we can embed the FLV files into SWF and play it. So, under some conditions, SWF file can be divided into two parts, the Flash Video (animation content) and the SWF player (Adobe Flash Player is commonly used to play the SWF).