Excerpt is a wordpress feature which will facilitate you to display a summary of the article on index pages automatically without requiring you to add a function readmore (more tag). However, this feature has a weakness, namely a picture in your article will not appear on index pages automatically.
Lucky, start from WordPress 2.9, theme authors can easily enable Post Thumbnail.
In this post we will learn how to make A post automatic excerpt and how to set post thumbnail.
Read More : Quick Tip : Make A Post Automatic Excerpt With Image Thumbnail on WordPress 2.9+