Explain the drift property found in an interest-rate model

What will be an ideal response?

The drift term refers to that variable in an interest rate model that captures the expected direction of the change in the interest rate (e.g., a short-term nominal rate referred to as the short rate). The symbol b is used in interest rate models to represent the drift. Various assumptions must be made about the drift term. For example, it can be assumed to be zero of some positive or negative value or it can be assumed to be dependent on the level of interest rates. If the drift term is assumed to be dependent on the interest rate, one can specify that it follows a mean reversion process where it returns to its long-run stable mean value.