hiya
secured means that if the loan is defaulted or cannot be serviced in terms of repayments or covering the interest that the house could be repossessed.
guarantor means that the loan payments and not the whole amount are covered. so if on a monthly basis you cannot pay the debt, then the guarantor would have to pay this amount.
the bank may let you have some of the loan unsecured and some either secured or guaranteed.
i cannot over emphasis, having been a bank manager, that you should get independant legal advice before securing 50000 against someone elses house.
i have seen these loans go wrong, but the majority are paid back.