A homepage is the front door of your entire business. It has to serve returning customers, investors, press, job seekers, and first-time visitors. To do that, it offers navigation, multiple sections, links to different parts of the site, and a broad message that covers everything you do. That is its job — orientation, not conversion.
A landing page is a single-purpose room with one door in and one door out. It exists to get one type of visitor to take one specific action: sign up, buy, download, book a demo. It has no navigation menu, no sidebar, no blog link, no "About us" detour. Everything on the page either advances that one action or does not belong there.
The confusion comes from the fact that both pages live on the same domain and both have a headline and a button. But they serve fundamentally different jobs, and treating one as the other costs real money.