An end node indicates that a particular path in a flow has come to an end. Once the assistant reaches an end node, it will prompt the user for feedback and then display the end node's summary text as a final message to the user. This completes the conversation, though users can choose to restart from the beginning if they need help with something else.
To avoid any surprises or undefined behavior, every path through your flow must eventually terminate in an end node. Avoid leaving dangling connectors.