How this is calculated
The principal-and-interest part of the payment uses the standard fixed-rate amortization formula:
M = P × [ i (1 + i)ⁿ ] / [ (1 + i)ⁿ − 1 ] — where P is the loan amount, i the monthly rate (APR ÷ 12), and n the number of monthly payments.
Property tax, insurance and HOA dues don't shrink your loan — they're recurring costs of owning, added on top and usually collected through escrow. That's why the payment breakdown shows them separately: on a typical 30-year loan they can be a quarter or more of the check you write each month.
What the amortization chart tells you
Early payments are mostly interest, because interest accrues on the whole outstanding balance. As the balance falls, each identical payment shifts toward principal. If the interest total surprises you, try the 15- or 20-year term — the payment rises, but total interest usually drops dramatically.
What this estimate leaves out
PMI (typically 0.3–1.5% of the loan yearly when the down payment is under 20%), closing costs, points, and rate changes on adjustable loans. Lender quotes will differ; use this to compare scenarios, not as an offer.