The document discusses key concepts related to mortgages including definitions of principal, interest, mortgage payment, amortization period, and term. It provides examples to calculate equity, monthly mortgage payments, and the interest portion of the first payment. Specifically, it defines a mortgage as a loan secured by property, calculates Harley's equity as $164,000, determines Meagan's monthly payment and that her first payment is mostly interest, and finds her equity to be $262,000.