Landing is Usually Performed in Two Variants:
This is a separate internal page on the site, which is not any different from other pages. We redirect visitors to this page if we would like to do them certain actions (buy, ask questions, give feedback, get quote, create account, etc.)
This is fully stand-alone site, simple and convenient, which have an expanded promotional offer, usually offer a minimum number of products / services (or even a single product / single service). So it is a site with full functionality, but fully oriented on one product / one service / one action.
Another feature of landing, as an independent site - all information is stored on one page, where you can easy navigate using scroll. By clicking on active menu, visitor simply toggles up / down the same page. Maximum simplicity - one of the factors due to which landing is becoming more popular, as the simpler and clearer resource, the more it will be targeted to users.
But behind the apparent simplicity of landing, in fact, it is a titanic work of whole team: designers, advertisers, creatives, artists, programmers, photographers, marketers are working to create a single page.