The first page decides when visitor will bounce off
Purely defining, a landing page is any web page that a visitor can “land” on. That means the first page that the user arrive on when he clicks on your link. However, when we talk in the terms of advertising and online marketing, a landing page can be made distinct from your actual website which is designed to achieve a single focussed objective.
That means, it has no navigation that ties it to the rest of the website. The reason for doing that is to let the visitors focus on that single objective and guide them towards your goal.