Hadoop and input informations divided in splits
All bigdata eco system works on something called parallel processing.

We have to process 100gigs of file. If we didnt split the file, then all the 100 gigs should be processed by single JVM(single map).

If we split the file into 1000 parts each of 100mb, then we can process each part with different JVM and apply the map function in less time.

MPP: Massively parallel Processing