A WordPress blog post consists of a handful of elements like the title and body but also tags, categories and comments. Tag pages usually display excerpts of all posts that use the same tag.
One example: If you search for Windows 7 Download on Google you find that a tag page for my website Windows 7 News is ranking on the third page of the results. Tag pages on the other hand are usually not the pages that visitors expect when visiting a website. (note: no longer)
Webmasters can utilize tag pages better on their WordPress blogs by creating so-called custom tag pages which can contain any information they want. If you open the Amazon tag page here on Ghacks for example, you will notice that it contains a custom description and image at the top before the actual articles are displayed on it.
WordPress provides the means to create those custom tag pages easily. Custom tag pages can be created in the theme directory of the WordPress directory by adding a new template file to the theme.
This new template file needs to begin with tag followed by the post slug of the tag. In the case of the amazon tag it would have to be named tag-amazon.php.
Custom tag pages have a higher priority than the default ones that show only excerpts of the posts. The easiest way to fill the custom tag with content is by making a copy of the tag.php file, rename that copy to tag-name.php, and fill it with custom data at the top.
WordPress looks for the following files in order to create those tag pages:
- tag-slug.php
- tag.php
- archive.php
- index.php
Look into your theme folder and see if there is a tag.php file. If it is copy its contents and create a new php file that is using the tag-slug.php as its name. If there is no tag.php look for archive.php and finally index.php.
Now simply add content to the file. It might take some experimentation at the beginning but it can be really worth it in the long run. If you have any questions or additions let me know in the comments.
Update: Some WordPress themes use tag descriptions automatically for this. If you fill out the description it may appear right above the tag even if you do not create custom tag pages. The Canvas theme that this site uses does so for example.