Landing Page
The landing page is the first page of a website that a person goes to. In the context of AdWords, it will always be the URL that is set up for the advertisement that the person clicks on. However, in the broader sense of digital marketing, the landing page could be a page that a different website is linking to or a page that is linked to from a social media post. You can compare the landing pages and sources of how a person got to that landing page in your Google Analytics account.
Read Google’s definition.