“A tag cloud or word cloud (or weighted list in visual design) is a visual depiction of user-generated tags, or simply the word content of a site, typically used to describe the content of web sites. Tags are usually single words and are normally listed alphabetically, and the importance of a tag is shown with font size or color. “
This is the definition of tag cloud from wikipedia. Tag clouds are usefull for a blog navigation. Tag clouds are replacing ta lists. The power of tag clouds comes from the ability to highlight most used tags.
Altough wikipedia says that it built to show to visitors what a site or blog is about, i think the main advantage is for navigation. For example you go to a website where you see on the homepage posts about notebooks, netbooks, tablets and phones and other miscelaneous technology related articles. Well, you are interested in tablets only, well, you go to the tagcloud and choose tablets. Or you are interested only in posts about ipad, you select ipad from there and you will get only ipad posts.
WordPress have a separate page for every tag defined by the article authors that appear in search results higher than single post pages. Why ? Because they have more information about a subject, they have the keyword in URL, the keyword in title, in h1 tag, everywhere. So, when you write a post, make sure you select tags wisely.
To add a tag cloud to your blog, go to Appearance -> widgets and drag and drop “Tag Cloud” widget to the sidebar. If wordpress says you don’t have any sidebar defined means your theme is a little messed up. Instead of trying to fix it, the best way is to manually add tag cloud directly to the template file.
In your sidebar.php file, or in the place where you want to add tag cloud, paste the following code: