Linear post navigation is an alternative to browsing entries by the calendar. For a given post, blojsom will determine the previous and next entries. If you are at the first entry, there is no previous entry. If you are at the last entry, there is no next entry.
Linear post navigation is a configurable property in your individual blog.properties file.
linear-navigation-enabled=true
If enabled, you can use the #NavigationLinks($homeText) macro in your template. A portion of Velocity template text is given below. The previous entry will be under the key, BLOJSOM_PERMALINK_PREVIOUS_ENTRY. The next entry will be under the key, BLOJSOM_PERMALINK_NEXT_ENTRY.