The SEO Settings is used to give a chance for the user to add meta author, meta description, meta keyword, and custom code to the whole pages. If you want to add meta author, meta description, and meta keyword in specific page, please read Page SEO.
Here’s how SEO Settings page looks like :
SEO Settings Editor
The meta author, meta description, and meta keyword will be added into HTML as the following code :
<meta name="keywords" content="Zeyn, wordpress template, template, wordpress">
<meta name="description" content="Launch your WordPress Site in Minutes">
<meta name="author" content="Djavaweb">
While custom code is used to add additional code to the whole pages such as Google Analytic code etc. this code will be added before the closing body tag.