TrackBack an open source system to communicate when one blog quotes another- so you can follow a thread. Similar to Pingback. When you post your related item- it checks all other users of your software (WordPress) and automatically posts a link to your thoughts on the subject. This sometimes slows your browser when you publish- as the trackback engine searches its database.
Pingback a method for web authors to request notification when somebody links to one of their documents. Typically, web publishing software will automatically inform the relevant parties on behalf of the user, allowing for the possibility of automatically creating links to referring documents.
For example, Alice writes an interesting article on her Web log. Bob then reads this article and comments about it, linking back to Alice’s original post. Using pingback, Bob’s software can automatically notify Alice that her post has been linked to, and Alice’s software can then include this information on her site.
Ping A notification to a blog tracking/search site like technorati notifying it that you have a new post. It uses RSS (really simple syndication) to announce you have new content. If this seems like Pingback and Trackback- the difference is that it just notifies, it doesn’t actually create a link back to your site.
Categories: This is how you group similar posts into a neat package for someone who comes to your site. A Post can be included in multiple categories. An example is a scooter shop that has multiple lines of scooters- each of these could be a category- like Vespa, Honda, Yamaha, Genuine. Then they could also include categories like New or Used. So if each post was about a scooter in their shop, you could quickly find all the used scooters, or all the Vespas. This is a poor man’s way to a true active database function. There may be a plug-in that allows you to select multiple categories.
The important thing to realize- is this category becomes yet another “page” to search engines- allowing your site to generate a big chunk of relevant data a different way than an individual page. Example, the scooter shop category Vespa becomes a “master page” with all the posts in that category- and the Category description becomes the page title. Categories are an easy way to increase the value of your site in search rank.