Big Data technologies helped companies to store and process tremendous data. There are many ways data can be processed and analyzed.
Developer can write program to tell machine to do certain processing of data and then analyzed as per the instruction given in the program. In this case computer processes the data and provide result as per the instruction given in the program. This is tradition way of programming.
But there one more technology which allows the computer to learn and take decision based on its learning. This is called machine learning. In Big Data machine learning is the processes of learning from the past data and then presenting predictions based on learning.
You can view detailed discussion at What is machine learning?.