The status bar consists of 4 areas, the Message Display, the Selection Display, the Project State Display and the Progress Bar.
The Message Display shows the progress messages while processing a command. When you skim through the menus you can see the tooltips of the menu items.
The Selection Display shows, whether you have selected a directory or files to operate on.
The Project State Display, which only is available in the Professional version, shows the Project State. For example, when 'Needs Update' is shown, new revisions are available in the repository and running an Update command on the project root directory will fetch them. This part of the status bar is also used to show ongoing refreshes of the meta-cache (see Refresh Meta-Cache) which are performed in the background to allow you to continue other operations.
The Progress Bar tries to give a hint about how long an operation will take. For some commands, like the Checkout command, SmartCVS cannot display a useful progress, because the file count is unknown.