Behavior Nodes
Behavior nodes work slightly differently than other nodes. While other nodes pull data, such as an Object pulling data from the output of a Geometry node, Behavior nodes execute forward-connected nodes through exec connections.
Events
Behavior execution usually starts with an Event node. Event nodes are executed when an event, such as the start of playback or a frame update occurs. When an event node is executed, it executes any behavior nodes connected to its exec output.