Apache Hadoop is an open-source framework that is used to efficiently store and process large datasets. This video will give you an overview of Hadoop: https://www.youtube.com/watch?v=n3qnsVFNEIU
Hadoop is used for storing and processing big data. In Hadoop, data is stored in inexpensive commodity servers that run as clusters. It is a distributed file system, which allows concurrent processing and fault tolerance. Hadoop consists of multiple software components for different functionalities such as:
- 
HDFS
 
- 
MapReduce
 
- 
Hive
 
- 
Spark
 
- 
HBase
 
- 
YARN etc.
 
Financial services companies use analytics to assess risk, build investment models, and create trading algorithms; Hadoop has been used to help build and run those applications. Retailers use it to help analyze structured and unstructured data to better understand and serve their customers.