A landing page or often also referred to as a splash page is a page that a visitor first lands on with the option to then proceed to the main website. Often landing pages are used for a number of reasons, such as promoting a particular product or service.
The advantages of creating a splash page allow you to design the page with that particular product or service in mind and tailor the content of the page to be very specific to the product or service you are promoting. It also makes it easier to optimise for the search engines as all the tags can be relevant.
If you use Google Adwords, you can create landing pages for your ads that are highly relevant to your Google Adwords ad group content. This will not only give the user a better experience but also allow you to improve your quality score, and a better quality score meaning you will be paying less for each click through.