Hadoop is used because it has the ability to store and process the huge volume of a variety of data. The Hadoop distributed computing model helps in increasing computing power. Hadoop is fault-tolerant because if any node is failed, then jobs are redirected to other nodes. Hadoop is more flexible since we do not need to pre-process the data before storing it and there is no limit for data storage. Hadoop is cost-effective and more scalable since we can simply add nodes if we need to add more data.
If you are interested to learn Hadoop, I recommend this Hadoop Certification program by Intellipaat.