Excerpt
A summary or brief teaser of your post featured on the front page of your site as well as on the category, archives, and search non-single post pages. Note that the Excerpt does not usually appear by default. It only appears in your post if you have modified the template file listing the post to use the_excerpt() instead of the_content() to display the Excerpt instead of the full content of a post. If so, WordPress will automatically use as the Excerpt the first 55 words of your post content or the content before the quicktag. If you use the “Excerpt” field when editing the post, this will be used no matter what. For more information, see Excerpt.
Send Trackbacks
A way to notify legacy blog systems that you’ve linked to them. If you link other WordPress blogs, they’ll be notified automatically using pingbacks. No other action is necessary. For those blogs that don’t recognize pingbacks, you can send a trackback to the blog by entering the website address(es) in this box, separating each one by a space. See Trackbacks and Pingbacks for more information.
Custom Fields
Custom_Fields offer a way to add information to your site. In conjunction with extra code in your template files or plugins, Custom Fields can modify the way a post is displayed. These are primarily used by plugins, but you can manually edit that information in this section.
Discussion
Options to enable interactivity and notification of your posts. This section hosts two check boxes: Allow Comments on this post and Allow trackbacks and pingbacks on this post. If Allowing Comments is unchecked, no one can post comments to this particular post. If Allowing Pings is unchecked, no one can post pingbacks or trackbacks to this particular post.
Password Protect This Post
To password protect a post, click Edit next to Visibility in the Publish area to the top right, then click Password Protected, click Ok, and enter a password. Then click OK. Note – Editor and Admin users can see password protected or private posts in the edit view without knowing the password.