Normally the secured obligation is a duty to return a loan or a loan given more responsibilities arising from the holding accessory, which are defined using three basic parameters:
The capital (or principal), which is the sum of money borrowed by the lender to the mortgagor. The debited amount of capital is usually less than the realizable value of mortgaged property, so that it can respond effectively reaching solutoria capital at public auction in the event of failure to pay all or part of the credit or loan is debited .
The deadline, which is the time it takes the return of capital and its ancillary. The loan repayment is made by periodic payments (usually monthly) to return the required capital plus all interest accrued during the time allowed to repay the principal.
The interest rate, which indicates an annual rate to be paid to the mortgagee (bank, savings bank, finance company, or individual) in respect of capital gains.
The interest rate may in turn be:
Fixed: It keeps its value throughout the term of the loan.
Variable: The value is reviewed periodically to adjust its value to the state of the economy. Usually some economic index is used as the Euribor, Libor or IRPH, which is added a differential so that the mortgage interest is always higher than the benchmark.
Once you know the three parameters are possible to perform the calculations to know which are the profits of the bank for the loan and what will be the amount we pay each month to repay it (returning the money to the bank).