The physical meaning of Laplace transform is to transform a time function f(t) into a complex variable function F(s), and vice versa. Time domain (t) variable T is a real number, and complex frequency domain F(s) variable S is a complex number. The variable s is also called "complex frequency". Laplace transform establishes the relationship between time domain and complex frequency domain (S domain). S=jw, where j is a complex unit, so the complex frequency domain is used. The popular explanation method is that because there are inductance X=jwL and capacitance X= 1/jwC in the system, its physical meaning is that the system H(s) has different attenuation for different frequency components, that is, this attenuation occurs in the frequency domain, so in order to distinguish it from the time domain, complex operation is introduced. However, in the complex frequency domain, the calculation form still satisfies ohm theorem, KCL, KVL and superposition method. Laplace transform is an important transformation in engineering mathematics, which mainly realizes algebraic operation of differential-integral circuit. It is recommended to refer to the book Integral Transformation. In first-order and high-order circuits, some problems are much more convenient to analyze in frequency domain than in time domain, and Laplace transform is a good analysis tool. It converts the signal input in time domain into the signal frequency input in S domain, and then from the output in S domain to the time-frequency output. It is simple and clear, and it can also analyze various changes of signals. Engineering mathematics or integral transformation can solve your problem. Well, in first-order and high-order circuits, some problems are much more convenient to analyze in frequency domain than in time domain, and Laplace transform is a good analysis tool. It converts the signal input in time domain into the signal frequency input in S domain, and then from the output in S domain to the time-frequency output, which is very concise and clear, and can analyze various changes of signals.