It's exactly what they have access to, though the landlord will usually be looking at credit to determine the tenant has a job and can pay, the background check is more useful to see if they have any tenant/landlord civil suits in their history.

Generally the more transparency there is on both sides, the better:

This way, the market can punish bad behaviors (abusive landlords / problematic tenants) and reward those who act properly.

Solid NPR rundown.

Thanks.