The WordPress page content editor includes a button in the toolbar to tell WordPress where you want an excerpt to end — the More tag. You can use the More tag for the default WordPress news archives or for the custom news template.
Place your text cursor in your news post where you want the More tag to appear and then click this icon. All the page content before the More tag shows in the excerpt. All the page content after the More tag shows only if the visitor clicks the link to read the full news post.
When you insert a More tag, a dashed line with a label will show up in Visual Mode in the WordPress content editor to indicate where the news post breaks between the excerpt and the rest of the news post.
In Code View of the page content editor, the More tag shows up as an HTML comment.