Confusion understanding parseval theorem?

1. What is the use of Parseval theorem?
2. What is parseval's theorem in DFT?

What is the use of Parseval theorem?

Parseval's Theorem states that the total energy computed in the time domain must equal the total energy computed in the frequency domain. It is a statement of conservation of energy.

What is parseval's theorem in DFT?

Parseval's theorem states that the energy of a signal is preserved by the discrete Fourier transform (DFT). Parseval's formula shows that there is a nonlinear invariant function for the DFT, so the total energy of a signal can be computed from the signal or its DFT using the same nonlinear function.