The first frame is where the top-level menu (the menu bar which is always visible) will be inserted. This is usually the top or left frame in a frameset configuration.

Top-level frame name:

The second frame is where the pop-up menus will appear. Please note that ALL pop-up menus MUST appear in a single frame. It's impossible to show pop-ups over different frames. This can be the same frame as the top-level frame.

Pop-up frame name:

The third frame is the default target for the menu links. This is the frame where links (URLs) defined by menu items (both top-level and pop-up) will be opened by default (you can set different targets for specific menu items in the properties window). This is usually the same frame as the pop-up frame but it can also be a special window name such as "_blank" (this will open all URLs in a new browser window), "_top" or "_parent".

Default target: