a graph is a more general-purpose concept which defines a set of related ops in a graph-like structure. a job is an instance of the graph which is configured to carry out a set of tasks in a particular context. this way you can define one graph which can be reused and configured in multiple ways - one use case of this could be to configure a dev job and a prod job from the same graph, using different resource definitions that point to different external dependencies like your prod database and your dev database.