TeX Live is an easy way to get up and running with the TeX document production system. It provides a comprehensive TeX system with binaries for most flavors of Unix, including GNU/Linux, and also Windows. It includes all the major TeX-related programs, macro packages, and fonts that are free software, including support for many languages around the world.
Some starting points for actually using TeX are in this introduction to the TeX world.
TeX Live has been developed since 1996 by collaboration between the TeX user groups. TeX Live was originally perpetrated by Sebastian Rahtz. Present miscreants include Akira Kakuto, Karl Berry, Luigi Scarso, Norbert Preining, Reinhard Kotucha, Siep Kroonenberg, Staszek Wawrykiewicz, and a cast of thousands.
Peter Breitenlohner passed away in October 2015. Peter was one of the foremost contributors to the TeX world for decades: he was the primary developer of e-TeX, dvicopy, and other programs, and in recent years, almost single-handedly kept the sources in TeX Live updated, integrating new versions and whole new libraries, reporting bugs, and so much more.
Sebastian Rahtz passed away in March 2016. He was the originator of TeX Live, among much other work with TeX at many levels for many years. He was involved with the UK TeX Archive, which led to CTAN, from which emerged TL. Later, he worked on XML and TEI, including some TeX integration efforts which survive today.
We miss you both, Peter and Sebastian.