SWF is the file format used by Macromedia Flash to deliver graphics, animation and sound over the Internet. Almost 95% of web users can view SWF content without having to install a new plug-in, and over 300 million people have downloaded the Flash player. Macromedia published the specifications for SWF in April 1998. This site has resources for programmers who want to read, write or play SWF files.
shockwave flash object files, animated pictures, often used for banners and adverts. can be viewed in IE or irfanveiw (amongst others) various programs can create them. other programs can be used to split them into their individual components.