I just started experimenting with graphene-django/GraphQL and am pretty confused about the relay library that has been brought in for graphene-django. After running through the cookbook example (implementing it with my own models) and running a test query, upon POST the query gets transformed to a strangely nested object with edges and nodes. What are these and what are they doing?

```
{
  companies {
    edges {
      node {
       id
     }
    }
  }
}

```