Other replies have good answers. Your monthly mortgage payment, depending on which type of program you aquire can include many things,i.e; principle and interest- is the most common if your loan is fully amortized. If you pay interest only, it would be the interest only. Your mortgage note and your truth and lending disclosure will have a breakdown of this for you. Other items that can be included in your payment would be taxes and your insurance. Your lender will have a seperate account set aside to accumilate the funds to pay on you behalf when the time comes. Mortgage Insurance or MI can also be in included.
One more additional item that may be included and can be the most important depending on your personal preference is a type of insurance that covers you incase of death or disability. Many people aquire this after the loan is done. Some Banks may have this service so please ask if it can be included and get a quote. This might make a difference in that unfortunate unknown of a death of a partner or spouse, God forbid.
Your have a valid question and I hope this helps. If you are looking for a refinance or to purchase a home, e-mail me at Manuel.Amaya@BBVACompass.com. I would love to help you in any way I can.