[en] The primary physics goal of the BaBar experiment is the systematic study of CP asymmetries in decays of the B⁰ and bar B⁰ into CP eigenstates. The secondary goals are to explore the wide range of other B physics, charm physics, τ physics, two-photon physics, and Υ physics that becomes accessible with the high luminosity of PEP-II. The design of the detector is optimized for the CP studies, but also serves well for the other physics opportunities. The critical experimental objectives to achieve the required sensitivity for CP measurements are: to reconstruct the decays of B⁰ mesons into a wide range of exclusive final states with high efficiency and low background; to tag the flavor of the other B meson in the event with high efficiency and purity; and to measure the relative decay time of the two B mesons. Studies carried out over the last few years at SLAC and for B factory proposals from other sites have led to a fairly complete picture of the performance requirements that the detector systems must meet