There are 4 different page types; "Standard" (regular page containing content), "Shortcut" (redirecting within the website), "Link to external URL" (redirecting to an external website) and "Folder" (a system folder used to store elements like news articles).
Read more about the Standard page settings on 2.2 Editing page properties.
The "Shortcut" page can be used to redirect the visitor to another page within the website, to avoid having the same content published on multiple pages, but there will still be a button in the menu. For example, say that you wish to have a contact page in a submenu, but you already have a contact page in the main menu, that contains all the information. Then you can create a shortcut page in the submenu and redirect it to the page in the main menu.
The settings consists of two functions, that need to be set. First you need to select what type of shortcut it should be (1). There is an option to redirect to a specific page (Selected page), redirect to the first available subpage or first subpage of a selected page (First subpage of selected/current page), randomize the selection of subpages of current or selected page (Random subpage of selected/current page) and finally for it to select the parent page of the current or selected page (Parent page of selected/current page). If you wish to select a page, use the search field (2) to type in the title of the page. (Img. 2.6.1)
The page type Link to external URL can be used to link to an external website. An example would be if you have a web shop on a separate installation/address, but still wish to have a section in your main menu called Web shop.
The settings consists of tree functions, that need to be set. First you need to select what type of protocol that should be used (1). This means what type of address it is; http:// (regular web address), https:// (secure web address), ftp:// (linking to a file transfer protocol), or mailto: (to link to an e-mail address). You can also set it to Auto to have TYPO3 automatically set the protocol. The second option is to add the web address (2). Because the protocol is set separately, you must add the URL without the protocol. The link will not work otherwise. Finally you need to tell TYPO3 that the link should open in a new window. Go to the tab "Behaviour" and add _blank in the field "Link target" (3). Save and the external link is ready. (Img. 2.6.2)