Snippets are buit into most of Notable's themes and can be accessed from the Wordpress Dashboard.
Snippets allow you to create a piece of content once and add it to multple pages or posts via shortcodes.
It's a great and easy way to post content (text, media, code, etc) that you use often via a Wordpress shortcode.
A simple example is an email signup form. You could create a snippet with your email signup form which assigns it to a shortcode. Then all you need to do is copy/paste the shortcode to your posts or pages.
A huge benifit of using a snippet is being able to update the snippet once and anywhere you used the shortcode will display the new content. So using our email signup example, if you wanted to update your text, you only have to do it once.