Keras is a high-level, deep learning API developed by Google for implementing neural networks.
Written in Python, it is used to make the implementation of neural networks easy.
Keras is relatively easy to learn and work with because it provides a python frontend with a high level of abstraction while having the option of multiple back-ends for computation purposes. This makes Keras slower than other deep learning frameworks, but extremely beginner-friendly.
Here’s a great class by Simplilearn to help you get started.