In this paper, the authors discuss about the big data. They analyze and reveal the benefits of big data. They analyze the big data challenges and how Hadoop gives solution to it. This research paper gives the comparison between relational databases and Hadoop. This research paper also gives reason of why big data and Hadoop. The people live in the age of data. It is not easy to measure the volume of data. According to the IDC estimate, the size of "Digital world" is about 0.16 zetta-bytes and forecasting the "Digital world" will grow by a factor of 300, from 130 exa-byte to 40,000 exa-byte.