If you left click on an item in Konqueror's window it will be "activated". Thus
Left click on an icon in the Toolbar to do whatever that icon is supposed to do.
Left click on an item in the Menubar to make that menu drop down.
Left click on a menu item to do that thing.
Left click on a link in a web page to make Konqueror follow that link.
Left click on a directory icon or name and Konqueror will descend into (show the contents of) that directory
Left click on a file name or icon and Konqueror will do whatever it thinks appropriate, based on the file type. In general this means opening HTML pages, or previewing text, image or Koffice files, embedding them within Konqueror's window. ("Preview" means that you can see the file but not change it).
Konqueror decides what the file type is by matching the filename extension against against a list of known types. If that fails it tries to guess the type from the file contents. You can change the list of known file types and associated actions and add new types, see the section File Types and Associations.
Clicking the middle mouse button on a file or directory name or icon does essentially the same as left clicking except that it does it in a new Konqueror window.
 | To see what the right mouse button does, see the section Right Mouse Button Menus. |