If you have two web pages page1.htm and page2.htm and you want to put a link on page1.htm to link to page2.htm and you only want those who know a password to be able to follow the link then you add the password gate to page1.htm and configure it with the desired password and specify page2.htm as the destination.
If someone enters the correct password on page1.htm then they will be taken to page2.htm just as if thery clicked on a link. If anyone enters the wrong password they will not get to page2.htm using the password gate.