A resistor, an inductor, and a switch are all connected in series to an ideal battery of constant terminal voltage. what does the time constant for the circuit represent?

In physics and engineering, the time constant usually denoted by the Greek letter τ, (tau), characterizes the frequency response of a first-order, linear time-invariant (LTI) system. Time constant of an RC circuit is the product of R and C. Time constant of an RL circuit is equal to inductance divided by resistance.