Write[channel, , , ... ] writes the expressions in sequence, followed by a newline, to the specified output channel.
The output channel can be a single file or pipe, or list of them, each specified by a string giving their name, or by an OutputStream object.
Write is the basic Mathematica output function. Print and Message are defined in terms of it.
If any of the specified files or pipes are not already open, Write calls OpenWrite to open them.
Write does not close files and pipes after it finishes writing to them.
By default, Write generates output in the form specified by the setting of the FormatType option for the output stream used.
See The Mathematica Book: Section 2.11.3.
See also: Print, Export, Display, Message, Read, LinkWrite.