The ALICE experiment at the CERN Large Hadron Collider (LHC) is a major facility designed to study high-energy nuclear collisions, particularly heavy-ion collisions between lead nuclei. This paper provides an overview of the ALICE apparatus, its performance, and the data handling procedures during the first physics campaign from 2009 to 2013. The ALICE apparatus, weighing approximately 10,000 tons, is optimized for central Pb-Pb collisions and features a high granularity and good particle identification capabilities. The paper details the central-barrel detectors (ITS, TPC, TRD, TOF, PHOS, EMCal, and HMPID), forward detectors, and the MUON spectrometer, highlighting their design and capabilities. It also discusses the beam conditions, including beam parameters, machine-induced background, and luminosity determination through van der Meer scanning techniques. The paper covers data taking, trigger systems, and calibration strategies, emphasizing the importance of background rejection and the use of control data for validation. The performance of the detectors and analysis methods for various physics observables is discussed, including centrality, event plane, jet reconstruction, hadron and electron identification, photon reconstruction, and muon reconstruction. The paper concludes with a summary of the physics goals and an outlook for future developments.The ALICE experiment at the CERN Large Hadron Collider (LHC) is a major facility designed to study high-energy nuclear collisions, particularly heavy-ion collisions between lead nuclei. This paper provides an overview of the ALICE apparatus, its performance, and the data handling procedures during the first physics campaign from 2009 to 2013. The ALICE apparatus, weighing approximately 10,000 tons, is optimized for central Pb-Pb collisions and features a high granularity and good particle identification capabilities. The paper details the central-barrel detectors (ITS, TPC, TRD, TOF, PHOS, EMCal, and HMPID), forward detectors, and the MUON spectrometer, highlighting their design and capabilities. It also discusses the beam conditions, including beam parameters, machine-induced background, and luminosity determination through van der Meer scanning techniques. The paper covers data taking, trigger systems, and calibration strategies, emphasizing the importance of background rejection and the use of control data for validation. The performance of the detectors and analysis methods for various physics observables is discussed, including centrality, event plane, jet reconstruction, hadron and electron identification, photon reconstruction, and muon reconstruction. The paper concludes with a summary of the physics goals and an outlook for future developments.