A Blog Layout in Joomla! has 3 main areas: Leading, Intro, and Links. These are shown in the diagram below.
Articles in the Leading Area always display in one column, using the full display width. Articles in the Intro Area may display in one, two, or three columns, depending on the Columns setting. The parameters below control the number of Articles in each area and the order in which they display. If an Article has a "Read more..." break, only the text before the break (called the Intro Text) will display, along with a "Read more..." link.