Many books and articles on graph databases talk about "embedded mode" and "single server mode".
For example, the Wikipedia article on graph databases mentions the following:
Blazegraph supports high availability (HA) mode, embedded mode, single server mode.
What do "embedded mode" and "single server mode" mean?
In the Embedded mode, Neo4J can be invoked or run in another application which is not standalone Neo4J. For instance, if you have a Python / Django app, you can 'embed' Neo4J but calling for Neo4J libraries.
In the Single server mode, the Neo4J and its applications works alone, for instance, like a recommender system or outlier detection. In this case, Neo4J may not have any dependence on other applications.