Earning Points. Starwood's Preferred Guest program is fairly straightforward: the more nights you spend at participating hotels, the faster you'll earn a free night.
As seen in the EXECUTING phase, the map will write (using Mapper.Context.write()) its output into a circular in-memory buffer (MapTask.MapOutputBuffer). The size of this buffer is fixed and determined by the configuration parameter mapreduce.task.io.sort.mb (default: 100MB).
The number of files inside the input directory is used for deciding the number of Map Tasks of a job. The Application Master will launch one MapTask for each map split. Typically, there is a map split for each input file.