In REST, nested resource is a web resource composing another. Its reference is built over the reference of another web resource.
Definition
In REST-style architecture , a resource is simply a source of information, the one you want to expose. The resource is referenced by a global identifier such as an URI. When you deal with information structure such as composition, you’ll use nested resources. The reference of the embedded resource is then built over the reference of the composite resource.
For instance, a blog post http://example.com/posts/1 owns several comments http://example.com/posts/1/comments.
