A nice video presentation of what Hadoop is, by Doug Cutting, the father of Hadoop.
Apache Hadoop started as batch: simple, powerful, efficient, scalable, and a shared platform. However, Hadoop is more than that. It’s true strengths are:
Scalability – it’s affordable due to it being open-source and its use of commodity hardware for reliable distribution.
Schema on read – you can afford to save everything in raw form.
Data is better than algorithms – More data and a simple algorithm can be much more meaningful than less data and a complex algorithm.