Machine learning, by its definition, is a field of computer science that evolved from studying pattern recognition and computational learning theory in artificial intelligence. It is the learning and building of algorithms that can learn from and make predictions on data sets. These procedures operate by construction of a model from example inputs in order to make data-driven predictions or choices rather than following firm static program instructions
We need machine learning in the following cases:
Human expertise is absent. E. g. Navigating on Mars.
Humans are unable to explain their expertise. E. g. Speech Recognition.
Solution changes with time E. g. Temperature Control.
Solution needs to be adapted to particular cases. E. g. Biometrics.
Problem size is too vast for our limited reasoning capabilities. E. g. Calculating webpage ranks.