TensorFlow (TF) is quickly becoming the technology that powers many DL applications. There are other APIs, such as Theano, but it is the one that has gathered the greatest interest and mostly applies to us. Overarching frameworks, such as Keras, offer the ability to deploy TF or Theano models, for instance. This is great for prototyping and building a quick proof of concept, but, as a game developer, you know that when it comes to games, the dominant requirements are always performance and control. TF provides better performance and more control than any higher-level framework such as Keras. In other words, to be a serious DL developer, you likely need and want to learn TF.
TF, as its name suggests, is all about tensors. A tensor is a mathematical concept that describes a set of data organized in n dimensions, where n could be 1, 2 x 2, 4 x 4 x 4, and so on...