Blocks are abstract units of mark-up that, composed together, form the content or layout of a web page when using the Gutenberg editor in WordPress.
The block editor is a modular approach to pages and posts – each piece of content in the editor, from a paragraph to an image gallery to a headline, is its own block. And just like physical blocks, WordPress blocks can added, arranged, and rearranged, allowing WordPress users to create media-rich pages in a visually intuitive way without needing to code custom HTML.
Information Partner ‘fragments’ typically consist of one ‘block’ – e.g. a paragraph of text.
You can try out a Gutenberg Demo page here https://frontenberg.tomjn.com/.