@sonam, Machine learning is the ability of a system to automatically learn and improve or modify based on the past experiences without being explicitly programmed. Machine learning focuses on developing various computer programs which can access data and use it to learn for themselves. In simple words, machine learning can be defined as the art of teaching a computer program to react or to recognize patterns.
Applications of machine learning code-
1. Virtual Personal Assistance
Example- siri,alexa,Google home
2. Predictions while commuting
3. Video Surveillance
4.Social Media Services
It actually depends from algorithm to algorithm .There are some examples where the code gets actually modified like genetic programming .On the other hand, Neural networks also modify parameters itself to provide the expected response.