Read more tag. it´s an easy way to show a short part of a very long post text.
It´s very easy, just locate in at the end of the paragraph and click in the ream more button in the entry text editor.
Here you can see how the resume in the post list looks like:
Excerpt. The excerpt content is very useful. It help you write a new and different text resume of your post, it´s a good way to promote your content.
This is how your post list resume will look like
NOTE: if you are not using excerpt or read more tag the theme will show the last 150 characters from your content automatically.