E.L.F stands for "Elf Learning Framework". It's a popular framework for building machine learning models that was developed by Google Brain. The E.L.F framework was developed to make it easier for developers to build and train deep learning models, and it has since been used to build a wide range of models in various fields, including computer vision, natural language processing, and more. The E.L.F framework is open-source and available for anyone to use and modify, making it a popular choice among machine learning developers.