A 'fixed interest' investment is where you loan money (typically to the Government or an individual company) in return for a fixed amount of income (or interest) over a particular time period. If you keep the investment, at the end of the time period you will normally (but not always) get all your money back. You will also usually receive regular interest payments.

Although prices on fixed interest investments go up and down as interest rates change, you do know that you will be receiving 'x' amount of income per year for 'y' years. As a result a fixed interest investment is usually considered to be less risky than equities.