Bonds are one type of fixed income security. They pay a fixed interest rate at a fixed security date(s) if you hold them to maturity. In between the maturity date(s) bonds are often traded something like stocks or derivatives. That sort of trading is in anticipation of interest rates going up or down. If you own a bond issued at a high interest rate that has yet to mature and rates go down, it is all of a sudden worth more. The opposite holds true as well.

I know fixed incomes are payments made through a specific schedule. But can someone explain how bonds can do that? I was under the impression bonds were investments that appreciate over time.