Ephemeral State
Graphs have a boolean value representing their ephemeral state, and this state is exposed to graph logic through the Ephemeral. A graph is in an ephemeral state when parameters are actively being configured/adjusted. For example, when one is dragging a number slider in the parameter panel.
The ephemeral state can, for example, be used to lower detail and compute load when a user is configuring the graph.
For information on ephemeral state and subgraphs, see: Subgraph