This lecture introduces the Discrete Fourier Transform (DFT) as a change of basis, highlighting the mathematical setup with finite-length signals and the Fourier Basis for complex numbers. The instructor explains the concept of a change of basis as a change of perspective that can reveal insights, followed by a proof of orthogonality within the basis vectors. The lecture concludes by discussing the implications of having N orthogonal vectors as a basis for CN, emphasizing the need for normalization.