In Gutenberg (the Block Editor project for WordPress), a block is a section of content in the post/page editor screen.
In the WordPress editor, a block is a content element that you can use to create pages and posts.
It can be a paragraph, an image, a video, a quote, a list, or any other type of content. Blocks are the building blocks of the WordPress editor and can be easily added, removed, and rearranged to create different layouts and designs.
With the introduction of the block editor in WordPress version 5.0, content creation has become more flexible and intuitive, allowing users to create rich, multimedia pages and posts with ease.