what are tags?

Tags are little keywords or phrases, which describe the content on the page. Basically, they are labels for the content. If you click one of these labels you will see a list of content which also uses that label. It's a great way to find similar content.

what is a tag cloud?

A tag cloud is a page which shows all of the tags used on the site. The more common a tag is, the larger it appears in the tag cloud. So at a glance you can see the most commonly used tags. If you click a tag, the site will show you a list of all the pages which use the tag. It's a simple way to quickly see what the site is all about, and find content by the labels it uses.