Mortgage Repayments

Diddlydewdrop

Hi,
I'm sure I will have asked this question of someone, somewhere before and it's probably a very obvious and straightforward answer but right now I can't get my head round it so I hope someone will help me.
I have a variable rate repayment mortgage.  I make monthly repayments based on the current rate so it can go either way.  
So if I'm paying interest in my monthly mortgage repayment why am I also paying an additional monthly, separate sum of interest?

Thrugelmir

The interest on your mortgage account is charged monthly, normally at the end of the month. At the beginning of the following month you pay this interest plus an element of the capital of the capital balance owed on the mortgage. As the capital balance reduces so does the interest charged. Resulting in more of your monthly payment paying down capital. 
The majority of your mortgage capital balance will be repaid in the later years. The longer the mortgage term the greater the amount of interest you'll pay.