What a landing page is and when you need one
A landing page is a one-page site with a single job: turn a visitor into an enquiry. No menu with ten sections, no «about us» for the sake of it. Only the path from the customer's problem to the button.
You need one in three cases: you are launching ads and need a page for a specific query; you are releasing a new product and want to test demand; you are running a time-limited promotion.
If the task is to present the company as a whole — services, cases, team — a landing page will not be enough. Then you need a corporate website.