PITI
Principal, Interest, Taxes, Insurance — the four components of a mortgage payment.
Principal and interest pay down the loan and the lender's profit. Property taxes and homeowner's insurance are typically escrowed by the lender and paid on your behalf.
When affordability tools quote a 'monthly payment,' they usually mean PITI. Add HOA dues, mortgage insurance (if applicable), and utilities for the true cost of living in a home.