There are 3 loan payment methods:
1) Equal Payment : equal payment in every month. This mode support an additional feature "Add per month"/"Add per year". This is the amount of additional payment you want to pay more every month or every year.
Note that "Monthly Payment" displayed result in "Equal Payment" input tab does not reflect the amount of "Add per year". However, "Payment" field in Detail Loan Schedule reflects "Add per year" amount if that month is first month of the year.
Also, in results, beside "Monthly Payment", "Total Interest" and "Total Payment", you also see the "Saving Interest" which means interest you can save by adding "Add per month"/"Add per year" and "Early Payoff" which is number of years or months that you finish the loan payment ahead of initial schedule. If you do not want to add "Add per month"/"Add per year", leave those fields blank.
2) Equal Principal: pay an equal amount of principal every month. Monthly interest is calculated based on current balance. Monthly payment is the sum of month principal and monthly interest.
3) Interest Only: pay interest every month and pay the loan in the last month of loan schedule.