What is the Apache Hadoop?

=> Solutions for Big Data. 
It's deals with complexities of High Volume, Velocity and  Variety of data.

=> Set of Open Source Projects. 

=>Transforms commodity hardware in to services that 

It's stores petabytes of data reliability
Allows huge distributed computations.

=>Key Attributes.

It's redundant and reliable.
Extremely powerful.
Batch processing centric.
Easy to program distributed applications.
It's run on commodity hardware.