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The documentation that comes with the Tcl and Tk distributions is commonly referred to as the man pages or as reference documentation. The form of this documentations is a generally brief page describing a particular command, its arguments, and a description of what the command does.
Among the ways to access "the manual pages" are
Translated manual pages
The fundamental "charter" manpage is of course called Tcl (nickname "Endekalogue"). The Wiki Endekalogue page lists translations (of the Tcl reference page) to more languages.