They can be used as a starting point where you activate an entire pattern and then modify the pieces that don’t quite work for you or as a sort of inspirational catalog of design elements for you to build your own patterns from.
So, where do these block patterns come from? Who created them? As with most things in WordPress, the answer is lots of places. Some patterns are included with WordPress by default, and there are also sometimes specialized block patterns that are bundled with a particular theme or plugin. There’s also a pattern library that includes both curated block patterns and all the patterns that are created and shared by the WordPress community itself.
So from the CMS, from themes, from plugins, from designers, from hobbyists, from people who just like love creating things and putting it out in the world, that’s, that’s where those patterns come from. But you can also create and curate your own block patterns, either to share back to the community as some folks do or because you are a site administrator and everyone needs to be able to add, I don’t know, an author block or something. But you don’t always want to be the one that has to put the photo on the page.