Big data refers to large volumes of structured and unstructured data that can be analyzed to reveal patterns and trends. It is characterized by 3 Vs - volume, velocity, and variety. Hadoop and associated tools like HDFS, MapReduce, Hive and NoSQL databases are used to handle big data. These tools provide scalability, flexibility and support both structured and unstructured data. Understanding big data analytics provides opportunities in data science and IT jobs and benefits industries like banking, healthcare, manufacturing and more through real-time insights.