Here is a list of new HTML5 tags that were not present in previous versions of html like xhtml 1.1 or html4.
Other articles in this series about new HTML5 tags are "HTML5 new tags and old tags with new behavior: ruby, rt, rp, bdi, wbr, canvas, command, menu, details, summary, datalist, keygen, output, address, div" and "HTML5 new tags: video, track, embed, object, mark, progress, meter, time".
Can I use the new HTML5 now?
Yes you can, but you need to use the HTML5shiv javascript for IE lower then version 9, or use modernizr where the HTML5 shiv is built in. The shiv script is a little javascript that enables HTML5 in browsers older then ie9. The advantage of using the new HTML5 right now is the semantic plus they will give you, it's always good to add semantic value to content because it can enhance your SEO quality.