Texdoc helps you find and view documentation in TeX Live. Its primary function is to locate relevant documentation for a given keyword (typically, a LaTeX package name) on your hard disk, and open it in an appropriate viewer.
You can browse texdoc's documentation online: user manual (pdf) and short man page (pdf, html).
Texdoc is part of the TeX Live distribution. (A
texdoc command is available in MikTeX, but it is actually a shortcut for
another program: mthelp, developed independently.)
The texdoc mailing list is available for bug reports (including finding the wrong file for a particular keyword), feature requests, patches, etc. You don't need to subscribe to the list in order to post a message and receive the replies.
Texdoc's development is hosted on GitHub. Here are download and installation instructions for Unix and Windows.
Texdoc is currently developed by Manuel Pégourié-Gonnard. Previous versions
with contributions from Reinhard Kotucha. First texlua versions
by Frank Küster. Earlier shell script versions by Thomas Esser, David
Aspinall, and Simon Wilkinson.
Texdoc is free software. It is distributed under the terms of the GNU GPL as of version 0.42. Earlier versions were in the public domain.