In your WordPress blog’s Dashboard, you can find a tab called Plugins. Plugins are utilities and custom-written WordPress add-on programs that extend the functionality and features of your blog.
Plugins can either enhance your comments form by adding a subscription option (Subscribe to comments plugin), or by displaying your commenter’s latest posts (CommentLuv plugin). You can also display your Top Commenters/Commentators or Recent Comments and posts on your sidebar (by using the widgets functionality).
You can also embed a YouTube video (Gecko Tube plugin) or embed any HTML code (video, ads, etc.) using the EmbedIt plugin. You can also block SPAM comments by activating the AKISMET plugin, or make your blog ranks well in the search engines by using the All-In-One-SEO plugin.