Basically the integral transforms used to transfer the function from the time domain to frequency domain and vice versa. For example for those transform techniques, Laplcae Transform, Fourier transform, Z-transform, Poisson Transform, ...etc. However, why do i need to change back and forth from Time domain to Frequency domain and how can i judge the necessity for conversion??

Note:- I'm more concern about this topic from Electrical engineering perspective.

Looking Forward

Thank you in advance