HTML stands for Hypertext Markup Language. HTML is a standard of syntax or language and is a way of describing to an internet web browser how to display text, colors, images etc. to form a webpage.
The HTML marquee is a non-standard tag for displaying scrolling text. The HTML marquee was originally designed by Microsoft for their Internet Explorer. Although the HTML marquee is still supported by most mayor browsers, the use of the HTML marquee is in most cases replaced by newer technologies like flash. In the end it should be stated that the HTML marquee does not allways render everywhere and does not allways render correctly. The HTML marquee remains a simple way of displaying announcements or to highlight things on a page.