On "Flash" or "Video" you can add multimedia (moving picture/animations) to the media libarary and then attach it to a CMS page. Adding flash or video works the same way as adding files or pictures. You just need to give the flash or video file the right width and height so that it will show properly on the site.
Flash is mostly used to animated banners and campaings. Flash file format is Shock Wave Flash and the extension is .swf
Videos are a great way for adding extra information about your business. Video must be x264 (H.264/MPEG-4 AVC) encoded and in F4V, MP4, M4A, MOV, MP4V, 3GP or 3G2 file video formats.