This article provides a comprehensive survey on near-field communications (NFC), a promising technology for future wireless systems. It explores the fundamental operating principles, channel modeling, performance analysis, signal processing, and integration with other emerging technologies. The paper highlights the unique properties of NFC compared to far-field communications, emphasizing its potential to enhance wireless network capacity through increased spatial degrees of freedom (DoFs). The article discusses deterministic and stochastic near-field channel models for spatially-discrete (SPD) and continuous-aperture (CAP) antenna arrays, and reviews existing contributions on near-field performance analysis, including DoFs, power scaling laws, and transmission rates. It also covers signal processing techniques such as channel estimation, beamforming design, and low-complexity beam training. The integration of NFC with technologies like MIMO, reconfigurable intelligent surfaces (RIS), and fluid antennas is examined, identifying key research opportunities for next-generation networks. The paper concludes with a detailed overview of near-field channel modeling, unique properties of the near-field region, and the application of electromagnetic information theory (EIT) in analyzing DoFs and effective DoFs (EDoFs). The work aims to inspire future research and development in NFC, highlighting its significance for 6G wireless systems.This article provides a comprehensive survey on near-field communications (NFC), a promising technology for future wireless systems. It explores the fundamental operating principles, channel modeling, performance analysis, signal processing, and integration with other emerging technologies. The paper highlights the unique properties of NFC compared to far-field communications, emphasizing its potential to enhance wireless network capacity through increased spatial degrees of freedom (DoFs). The article discusses deterministic and stochastic near-field channel models for spatially-discrete (SPD) and continuous-aperture (CAP) antenna arrays, and reviews existing contributions on near-field performance analysis, including DoFs, power scaling laws, and transmission rates. It also covers signal processing techniques such as channel estimation, beamforming design, and low-complexity beam training. The integration of NFC with technologies like MIMO, reconfigurable intelligent surfaces (RIS), and fluid antennas is examined, identifying key research opportunities for next-generation networks. The paper concludes with a detailed overview of near-field channel modeling, unique properties of the near-field region, and the application of electromagnetic information theory (EIT) in analyzing DoFs and effective DoFs (EDoFs). The work aims to inspire future research and development in NFC, highlighting its significance for 6G wireless systems.