Hullo Vmilli,
In my experience, good HR means a person who contributes to the business and for that to happen you have to a) first understand each and every job - what they do and how they do it and b)how each job contributes to organizational Vision / Mission / profitability drivers / - delivery, revenue, cost, customer service, quality etc. Of course you have to go into the depth of each job.
At the intersection of the job & it's linkage to organizational goals, you will find the KPIs.
Let me know if this helps.
Geet