A landing page is a standalone web page that a person "lands" on after clicking through from an email, ad, or other digital location.
Once they’re on your landing page, users are encouraged to take an action, such as joining your list or buying your products. If the user takes the specific desired action, then your landing page has succeeded in getting them to convert.
Typically, landing pages only encourage their users to take one such action, like to fill out the custom signup form on the page.