What exactly is Principal & Interest (P&I) anyways?
All mortgage payments are divided into two different parts:

Principal
The principal is the amount you return to the lender for the actual dollars that you borrowed. Because the principal is based on the amount of money that you actually borrowed, it remains fixed for the entire life of the loan, but is reduced proportionally with each payment. You will never pay back more principal than you borrowed initially.

Interest
The interest that you will be charged can vary however it will depend on interest rate market conditions, and the type of mortgage that you receive. There are two primary types of interest rates: fixed rates and adjustable rates. A fixed rate is one that is set at the time of purchase. With a fixed interest rate you lock in the interest rate for the entire term of the loan. With an adjustable rate, the interest rate you pay changes as national interest rates move up or down. Although adjustable rates present some risk, they usually offer a lower initial interest rate than a fixed rate.