Where you have owned property for a period, you may have generated equity in the property.
That equity may be sitting "idle", as it may not be generating a return.
You may also have a credit card that is attracting interest at a rate of, say, 16% per annum.
By using the equity in your property to secure a loan at, say 6% per annum and using that loan to repay your credit card, you are saving 10% per annum. Over time, you will save a significant amount.