Machine learning is a subfield of artificial intelligence (AI) that enables computers to learn from data and improve their performance on a specific task without being explicitly programmed. It has become a crucial technology in today's world, and its applications are virtually limitless.

Here are some reasons why machine learning is used:

1. Predictive analysis: Machine learning algorithms can be used to predict future outcomes based on historical data. For example, a company can use machine learning to predict which products will be popular in the future, allowing them to stock up on inventory in advance.

2. Personalization: Machine learning algorithms can be used to personalize user experiences. For example, a streaming service can use machine learning to recommend movies and TV shows that a user is likely to enjoy based on their viewing history.

3. Automation: Machine learning algorithms can automate repetitive and time-consuming tasks. For example, an e-commerce website can use machine learning to automatically categorize products based on their attributes, saving employees time and effort.

4. Fraud detection: Machine learning algorithms can be used to detect fraudulent behavior. For example, a credit card company can use machine learning to identify unusual patterns of spending that may indicate fraud.

5. Medical diagnosis: Machine learning algorithms can be used to assist in medical diagnosis. For example, a machine learning algorithm can analyze medical images to help doctors detect and diagnose diseases.

Overall, machine learning has numerous practical applications across a wide range of industries and fields, making it an important technology for businesses, researchers, and individuals alike.