Too Long; Didn't Read
GetStaticProps is part of NextJS' latest release version 9.3 and offers Next-gen Static Site Generation (SSG) Support. This is mainly useful for websites that use React/NextJS with a CMS integration. The content will be loaded from the CMS when a visitor gets to your website. If you have quite some content, it will take time to first load it, then process the JavaScript and ultimately render it. This will have an impact on your page-speed and therefore your SEO.