FileStream associated with the file, the class of the operational flow.
The first part has been introduced Stream, FileStream class inherits Stream.
Repeated once, the stream is a sequence of bytes in memory, represents all classes inherit from Stream stream class. There NetWorkStream, MemoryStream, GZipStrem and so on.
Is a sequence of bytes in the machine's memory, why should flow into so many categories it?
Associated with the file, byte sequences and sequence of bytes associated with the network, it is different! So, to be divided so much class. This is what I currently my understanding.