The a (short for "anchor") tag is the essential part of "hypertext." (In case you didn't know, I hate the term hypertext with a passion.)
A regular, decent a looks like this:
Yahoo <a href="http://www.yahoo.com/">Yahoo</a>
or like a collection of other variants, for people who despise regular underlined blue--or whatever is regular now. What we ultimately realize about new ones is that we really depise them.
Just think of it. You can link to anything, a website, a picture, a download, anything!--with that simple tag.
It's enough to make HTML a must.
Found something good? Make an "a" to it! Starting now.