Continual learning, also known as lifelong learning, aims to enable artificial intelligence systems to learn from a continuous stream of data while retaining previously acquired knowledge. Unlike traditional machine learning approaches that assume static datasets and offline training, continual learning faces unique challenges such as catastrophic forgetting, knowledge transfer, and scalability. Over the years, a variety of strategies have been developed, including regularization-based methods, memory replay techniques, and dynamic architectural adaptations. This survey provides a comprehensive review of continual learning, covering fundamental concepts, major learning paradigms, and state-of-the-art methodologies. We discuss the primary challenges that hinder the deployment of continual learning models in real-world applications and examine existing solutions, highlighting their strengths and limitations. Furthermore, we explore diverse application domains, including computer vision, natural language processing, and robotics, where continual learning plays a pivotal role in enabling adaptive intelligence. Despite significant progress, several open problems remain unresolved, necessitating further research. We outline future directions such as neuroscience-inspired learning mechanisms, meta-learning for rapid adaptation, scalable and efficient model architectures, and task-agnostic continual learning. Additionally, we emphasize the importance of ethical considerations, fairness, and security in developing responsible lifelong learning systems. By addressing these challenges, continual learning has the potential to revolutionize artificial intelligence, enabling autonomous systems to learn in an open-ended and evolving manner. This survey serves as a reference for researchers and practitioners interested in advancing the field and building more robust and adaptable AI models.