If someone buys a 10-year bond with a fixed rate of 10%, and a newly issued 10-year bond pays 12%, then the old bond paying 10% will have fallen in value.
Higher bond prices mean that the interest a buyer is willing to accept is lower than before.
When interest rates are high (low) and expected to fall (rise), demand for bonds is likely to be high (low) and money demand is likely to be low (high).