What did I learn today 2

What did I learn at this hour?
During my second hour, I learnt to use new terms such as ul, ol, !doctype, nav, a. The !doctype is not a tag, it helps the browser know about the version of HTML or any other markup language that is being used in the document. "ul" and "ol" are used to list things, with "ul" means unorder list and "ol" organizing list. Last but not least, "nav tag" is an element that represents a part of a page whose purpose is to provide navigation links. Finally, "a" tag defines a "hyperlink", which is used to link from one page to a new one.