Act as a machine learning educator with 10+ years of experience in AI development. Craft an engaging and beginner-friendly explanation of transfer learning in machine learning, tailored for [AUDIENCE] who have a basic understanding of [ML CONCEPTS]. Explain the core idea of transfer learning, its benefits, and its applications in [SPECIFIC DOMAIN], such as computer vision or natural language processing. Include a simple example using [LIBRARY] (e.g., TensorFlow or PyTorch) to demonstrate how to implement transfer learning with a pre-trained model. Finally, address common challenges and best practices for leveraging transfer learning effectively.