Transfer learning has emerged as a pivotal technique in artificial intelligence, particularly within deep learning, due to the growing availability of large datasets. It enables AI models to leverage pre-trained knowledge from one task to enhance performance on a related but distinct task, often requiring smaller datasets and fewer training epochs. Common applications include computer vision and natural language processing, where models like VGG, ResNet, and BERT are frequently employed. By reusing weights and biases from pre-trained models, transfer learning facilitates both fine-tuning for specific tasks and feature extraction for broader applications. Despite its advantages, the technique faces challenges such as dataset bias, overfitting, and ethical concerns, necessitating careful consideration of domain similarity and transfer strategies. Future trends point towards continual learning, federated learning, and improved pre-training methods, alongside ethical advancements to ensure fairness and transparency in AI systems. Transfer learning's impact is evident across various industries, including healthcare, autonomous vehicles, gaming, and e-commerce, where it accelerates innovation by optimizing resource use and enhancing model accuracy.