Basically all signals are represented in standard amplitude over time format.
If you need to know the behavior of the signal in the frequency domain, that is
how the magnitude of the signal behaves over each frequency the signal is composed of, you have to obtain Fourier Transformation.
Now if you have a system and need the stability, you find the Z transformation.
That is z transform is applied to system functions and not signals.
Now comes Laplace transform,
Once again its applied to systems and not signals. In order to obtain the Laplace coordinates in complex time space we obtain L transform
Fourier- Frequency domain- Signals
Laplace and Z - Complex Space time - systems
Can u give any example of signal and the complex systems that u mentioned.If u hav any literature to exlain the difference it would be helpful.
regards
wajahat