Named after a subatomic particle, Gluon is an API over Amazon’s MxNet that was introduced by Amazon and Microsoft in October 2017. It will also integrate with Microsoft’s CNTK. While it is similar to Keras in its intent and place in the stack, it is distinguished by its dynamic computation graph, similar to Pytorch and Chainer, and unlike TensorFlow or Caffe. On a business level, Gluon is an attempt by Amazon and Microsoft to carve out a user base separate from TensorFlow and Keras, as both camps seek to control the API that mediates UX and neural net training.
To contrast Gluon with other frameworks, please see this deep learning framework comparison page.
Amazon’s Gluon should not be confused with Gluon, the company, which helps developers deploy mobile apps.