The industrial Internet of Things (IIoT) has become an innovative technology that has brought many benefits to industries and organizations. This review presents a comprehensive analysis of IIoT’s applications, highlighting its ability to optimize industrial operations through advanced connectivity, real-time data exchange, automation, and its importance in the context of Industry 4.0. Emphasizing the distinction between IIoT and traditional IoT, the paper explores how IIoT focuses on enhancing industrial ecosystems and integrating cyber-physical systems (CPSs). This article explains how to establish a highly linked infrastructure to support cutting-edge services and ensure greater flexibility and efficiency. It emphasizes the role of the CPS and industrial automation and control systems (IACSs) in realizing the potential of IIoT. Security concerns, an important part of IIoT, are addressed through conversations on protecting networked systems, assuring operational reliability, and emphasizing the need for strong security measures to prevent potential threats and vulnerabilities. Furthermore, critical technologies such as machine learning (ML), artificial intelligence (AI), and various communication protocols, including fifth generation (5G) and message queuing telemetry transport (MQTT), are investigated for their potential to improve system performance and decision-making processes. In addition, the article also discusses the safety precautions and challenges of using IIoT. Finally, the article emphasizes the importance of addressing security issues in promoting the successful adoption of the IIoT and achieving its expected benefits. This study offers valuable resources for researchers, academics, and decision-makers to implement IIoT in industrial environments.