Answer by user-needs-help for What's the difference between dependencies, devDependencies and peerDependencies in npm package.json file?

I found a simple explanation.

Short Answer:

dependencies"...are those that your project really needs to be able to work in production."

devDependencies"...are those that you need during development."

peerDependencies"if you want to create and publish your own library so that it can be used as a dependency"

More details in this post: https://code-trotter.com/web/dependencies-vs-devdependencies-vs-peerdependencies