In TYPO3 there are two basic types of shortcuts for menu/navigation items - shortcuts to internal pages and shortcuts to external URL's.
Shortcuts to internal pages are handy if for example you wish provide an easy to remember URL for your users or for print. Example: When a user enters domain.com/phdexam in his browser he is directly led to domain.com/studies/phd-school/qualifying-exam/
Create a page like you normally would - give it a page title as minimum, and choose "Shortcut" as page type.
A dialog will ask you to confirm this choice. After confirmation, switch to the "Shortcut" tab in the page properties, and click the folder icon to open the page tree.
Click the title of the page you wish to make a shortcut to. If you wish to link directly to certain content in the page (so called anchor links), click the arrow to the right of the page title, which will give you a listing of all named content elements on the page. Click the title of the content element to link directly to it.
Alternatively you can use "Shortcut mode", to make the shortcut go to first subpage or a random subpage of the page you selected in "Shortcut to page"