Equity release question

cd36uk

Hi

I hope this is posted in the correct section, as I wasnt sure where to put it, but here goes.

My parents (both retired) did equity release with Northern Rock back in 2002 for approx £35k. I have one sibling, they asked myself and my sister at the time if we minded them doing this (as it would be our inheritance). We both said it was their choice whatever they want to do with their house.
My knowledge of how equity release works is pretty non existant, and I would like to know more but do not want to upset or offend my parents by asking to what extent will this affect my half of the inheritance when they are no longer with us.

I know that they had the option to pay some back much like a loan but they declined and so the full debt is still outstanding.
So if someone could enlighten me, i would appreciate that.
What will happen when their home is sold (after death), will Northern rock get a lump sum based on an interest calculation? or is it a variable percentage of the house value at the time of sale?

thanks in advance