Unlike a homepage, which introduces a whole business and offers many paths, a landing page has one message and one call to action. It typically includes a headline that matches the ad or post that brought the visitor, the benefit in plain words, proof such as testimonials, a short form or button, and answers to the doubts people have before they act.
The match between promise and page matters most. If an ad offers a free guide and the page opens with a sales pitch, people leave. Fast loading, a layout that works on a phone and a form that asks only for what is needed all make a measurable difference, and A/B testing shows which version works better.