The integration of the Internet of Things (IoT) with cloud computing has emerged as a transformative paradigm for enabling scalable, flexible, and intelligent systems across diverse application domains. This systematic review examines the architectural models, enabling technologies, and communication frameworks that facilitate seamless interaction between IoT devices and cloud platforms. It explores how cloud computing provides on-demand storage, processing power, and analytics capabilities to handle the massive volumes of data generated by IoT ecosystems. The review highlights key components such as edge computing, fog computing, data streaming, and real-time analytics, which enhance system performance and reduce latency. Additionally, it analyzes the role of artificial intelligence and machine learning in extracting actionable insights from IoT data. Critical challenges, including data security, privacy, interoperability, latency, and scalability, are discussed along with emerging solutions and best practices. The study also evaluates various application domains such as smart cities, healthcare, industrial automation, agriculture, and transportation. The findings indicate that the integration of IoT and cloud computing significantly improves operational efficiency, decision-making, and service delivery, making it a cornerstone of modern digital transformation.