HTML (HyperText Markup Language) stands for Hypertext Markup Language. The goal of the language was to organize and manage content. In its most basic form, HTML enables you to create a page on the Internet. HTML code is what you write in order to post text, links, images etc., on your pages.
FLASH is a coded web language that enables the addition of animated content and video to a website. Flash files have the file extension .swf and need to be read by a Flash plugin in the navigator.