$$ H(f) = \int_{-\infty}^{\infty} h(t) e^{-j 2 \pi ft} dt $$ So, given either a system's impulse response or its frequency response, you can calculate the other. Either one is sufficient to fully characterize the behavior of the system; the impulse response is useful when operating in the time domain and the frequency response is useful when analyzing behavior in the frequency domain. h(t) here stands for the impulse response and H(f) stands for the frequency response. Also linking to an [excellent explanation] on dsp.stackexchange, where you can understand the process in much more detail in comparison to substitute by s. [excellent explanation]: https://dsp.stackexchange.com/questions/536/what-is-meant-by-a-systems-impulse-response-and-frequency-response