Today on (Ad)Word of the Day, we'll be covering landing page from the AdWords Glossary:
An active webpage where customers will 'land' when they click your ad. The web address for this page is often called a 'destination URL' or 'clickthrough URL.'
Your landing pages are most effective when they are consistent with your ads. For example, if your ad is for a specific product at a certain price, both the product and the pricing should be featured prominently on your landing page.

If you're not sure what landing page design works best with your customers, you can use Google Website Optimizer to try different pages to find the most effective one.