The purpose of a landing page is to build an email list to expand your online business.  Sometimes, a landing page is created to drive the visitor straight to a business website without signing up for an email list.  This is done with a CTA (call-to-action) button.  By clicking the CTA button, the visitor is taken directly to an external website to see what he is looking for.  CTA buttons are created, also to make the visitors sign up for a newsletter, download a free e-book or take part in a business Webinar.  A landing page must be created with great care to keep the visitor engaged.  In other words, a landing page is very useful in the case of visitor engagement.