I have spent several hours learning about modules and layers in Nuxt 3, but I'm unsure about the exact differences between them. With layers, we have the ability to share components, pages, composables, and configurations between multiple projects in a monorepo. On the other hand, modules also allow us to achieve this, but with an additional step of configuration. I would like to understand if there are any distinctions between them in terms of their use cases.
Think of modules as small pieces of code that you can use to achieve a specific task, like:
As you can see, those are small chunks either created by the community or the Nuxt Core team that allow you to achieve faster productivity.
Nuxt layers are meant to be used for extendability purposes, if you do have a Nuxt app and would like to create a new Nuxt project based on the first one without redoing the whole config/components/styling/etc.
Think about it as OOP's inheritance or TypeScript's extends pretty much.
The official docs are pretty good for that specific part: https://nuxt.com/docs/getting-started/layers
Now, you could also write your own Nuxt module and have a functionality that emulates the behavior of layers, which should be totally doable (it is probably how Nuxt layers are made internally anyway).
Hence, if you're an author, the details will mostly be implementation details.
If you're a regular user (as in consuming), Nuxt layers are a gentle entry into reusability without getting your hands dirty writing your own module.