A Landing Page is a standalone web page, disconnected from a website’s navigation, created for the sole purpose of convincing a visitor to act
In marketing terms, a landing page is a distinct page, preferably not on your website, that’s built for one single conversion objective. It's a page within your website built with a single actionable ask that facilitates the completion of that objective. Your landing page should be completely distinct from the rest of your website - with no navigation bar to distract your visitors from your sole conversion goal.
A landing page is a must if you are investing into search engine marketing, so that you can lead a click on your ad to a designated page specifically designed to encourage an action from the visitor like Lead generation or Relationship building
A landing page is also essential for you if you are selling stuffs online. A landing page is not your homepage. An E-commerce website should have multiple landing pages - one for each of its products. Each product landing page is for the single purpose of the product, and has a focused conversion Call to Action(CTA), to buy that product.