A landing page is a stand-alone webpage created specifically for a marketing or advertising campaign, it’s sole purpose is to persuade its reader to follow its “call to action”.
Here’s an example of a landing page: a business that collects excess waste from your home creates a landing page that is telling you exactly what they do, how it helps you directly, how much it costs, what they do with the waste etc. Their “call to action” would be to get you to use their services to clean your home.