This paper reviews Richard Feynman's landmark 1981 keynote at Caltech, where he proposed building a computer based on quantum mechanical principles to simulate physical systems. It begins with a biography of Feynman: a theoretical physicist, Nobel laureate, Manhattan Project participant, and a curious polymath (radio repair, lock picking, drawing, samba drumming). The paper introduces essential quantum mechanics: superposition (e.g., a photon simultaneously reflected and transmitted by a half-silvered mirror) and entanglement (measuring one particle instantly influences another, violating classical locality). It explains qubits as two-state quantum systems (|0⟩, |1⟩) existing in superposition until measurement, and evolutions as matrix operations that perform parallel computation on all superposed states. Quantum error correction is necessary due to extreme sensitivity to environmental noise. The historical context is traced from Maxwell's Demon and Landauer's erasure principle to Bennett's reversible computation, Benioff's hybrid quantum Turing machine, Deutsch's first quantum computing model, Shor's factoring algorithm (1994), and the 2001 7-qubit NMR demonstration factoring 15. Feynman's core argument: simulating quantum physics with a classical computer leads to exponential complexity (N^R configurations) or discretization errors (probabilities below 2^k become zero). He examines two approaches: (1) calculating probabilities numerically (ruled out by exponential growth), and (2) using a probabilistic computer (which only mimics nature unreliably and is constrained by locality). He proposes a Monte Carlo method but admits it fails to capture true quantum behavior due to entanglement. Feynman's revolutionary conclusion: to efficiently simulate quantum mechanics, one must build a computer that itself operates on quantum principles—a universal quantum simulator. This speech is recognized as the direct precursor to the modern concept of a universal quantum computer.This paper reviews Richard Feynman's landmark 1981 keynote at Caltech, where he proposed building a computer based on quantum mechanical principles to simulate physical systems. It begins with a biography of Feynman: a theoretical physicist, Nobel laureate, Manhattan Project participant, and a curious polymath (radio repair, lock picking, drawing, samba drumming). The paper introduces essential quantum mechanics: superposition (e.g., a photon simultaneously reflected and transmitted by a half-silvered mirror) and entanglement (measuring one particle instantly influences another, violating classical locality). It explains qubits as two-state quantum systems (|0⟩, |1⟩) existing in superposition until measurement, and evolutions as matrix operations that perform parallel computation on all superposed states. Quantum error correction is necessary due to extreme sensitivity to environmental noise. The historical context is traced from Maxwell's Demon and Landauer's erasure principle to Bennett's reversible computation, Benioff's hybrid quantum Turing machine, Deutsch's first quantum computing model, Shor's factoring algorithm (1994), and the 2001 7-qubit NMR demonstration factoring 15. Feynman's core argument: simulating quantum physics with a classical computer leads to exponential complexity (N^R configurations) or discretization errors (probabilities below 2^k become zero). He examines two approaches: (1) calculating probabilities numerically (ruled out by exponential growth), and (2) using a probabilistic computer (which only mimics nature unreliably and is constrained by locality). He proposes a Monte Carlo method but admits it fails to capture true quantum behavior due to entanglement. Feynman's revolutionary conclusion: to efficiently simulate quantum mechanics, one must build a computer that itself operates on quantum principles—a universal quantum simulator. This speech is recognized as the direct precursor to the modern concept of a universal quantum computer.