Understanding the Difference Between HR and Organizational Behavior: How Do They Connect?

I am unclear about the relation or difference between HR and Organizational Behavior.

Is there any difference between HR and Organizational Behavior (OB)? Or, is OB a function (like recruitment and selection or performance management) of HR?

As far as I know, HR audit is to identify the lapses, shortcomings, and gaps in the implementation of HR functions and suggest remedial actions, if any. So, if OB is a function of HR, then what is the observation of HR Audit about OB?

Mr. N.K.S has explained well, and I think it needs no more elaboration. For the sake of brevity, we can say that OB is theory, and HRM is practice.

HR Audit is a tool to evaluate the performance of the human resource department in an organization.