What is Keras?

This is a high-level API(written in Python) for creating Neural Networks.
Keras can run on top of other deep learning frameworks like TensorFlow, Theano, or Microsoft Cognitive Toolkit (CNTK).

Neural Networks(Keras) vs. Traditional ML Models(scikit-learn)

Neural Networks Traditional ML Models
Build using Keras scikit-learn
Structure Layers of interconnected neurons Depends on Model. Eg Decision Trees/Random Forests(Tree-based hierarchy)
Training Time Longer Less
When to Use LOTS of data, Working with Larger,complex non-linear patterns Tabular data, Working with smaller datasets