It’s the amount due now to you by the borrower(s).
This includes 3 components:
Remaining principal of the loan Month after month, this amount is decreasing after each installment repaid by the borrower. In case the borrower has some delay on the payment of his installment, the overdue principal is included in the remaining principal.
Overdue interest Existing only in case the borrower is in delay. This is the amount of interest due which has not yet been paid.
Accrued interest This is a small amount, equal to the interest calculated daily since the last due date of the borrower. We calculate daily interest but we charge the borrower only once per month, to be paid within the monthly installment. Between 2 installments, this amount is increasing everyday with the daily interest, then is coming back to zero on the due date when the installment has to be paid.
The outstanding amount is the key financial amount of the part of the loan. It’s the amount you pay when you buy (if you buy without extra cost or discount).
After having purchased a part of loan, the outstanding is evolving. It's usually increasing everyday with accrued interest, until the Due Date. On Due Date, if the borrower pays as planned the installment, the outstanding is decreased by the payment.