The difference between the Run and Debug buttons in Flow Builder is that the Debug button displays details for debugging the flow (D). Debug mode allows the flow designer to step through the flow, inspect variable values, and understand the flow's behavior at each step, which is crucial for identifying and fixing issues within the flow. The Run button, conversely, executes the flow without providing the detailed execution information that Debug mode does.Reference: Salesforce Help Documentation on Flow Testing and Debugging.