This document discusses the sampling theorem and its key aspects. It introduces the sampling theorem, which states that a signal can be reconstructed from its samples if it is sampled at least twice its maximum frequency. It then provides two statements that comprise the combined sampling theorem statement - that a signal containing frequencies up to W Hz can be determined from samples spaced 1/2W seconds apart, and recovered from those same samples. The document also mentions spectrums, aliasing effects, and using a low-pass filter to band-limit signals before sampling.