When I go to 'Perform Payments' for the landlord, what is the difference between the 'current balance' and the 'rent balance'?

When you go to 'Perform Payments' for the landlord, the 'current balance' refers to the total amount that includes all transactions, such as adjustments and rent payments. In contrast, the 'rent balance' represents only the total amount from rent payment transactions.

Further reading: iamproperty CRM Full Accounts Manual