Landing pages are used by marketers to help capture leads or as a click-through so that traffic is funneled to another page. These are also used to sell a product directly to your visitors without the need to browse for a certain product or service.
Landing pages are usually separate from the website they are hosted. They rarely us the same design as the website that sits on the root of the domain and there are hardly any navigation menu that links the landing page to the site and vice versa.
There are a number of ways in which you can use WordPress to create a landing page, here are some of those: http://www.elegantthemes.com/blog/tips-tricks/create-landing-pages-using-wordpress