What is Lamrim?
Lam Rim (Tibetan: lam "path", rim "stages") is a Tibetan Buddhist textual form for presenting the complete path to enlightenment as taught by Gautama Buddha.
In Tibetan Buddhist history there have been many different versions of the Lam Rim, presented by different teachers, of the Nyingma, Kagyu and Gelug schools. The Sakya have a somewhat similar textual form called the Lam Dre. However all the versions of the Lam Rim are based on extensions of Atisha's 11th Century root text 'A Lamp for the Path'.
When Atisha was invited and came to Tibet he was asked by Changchup Od to give a complete and easily accessible summary of the doctrine in order to clarify wrong views - especially the apparent contradictions found across the Sutras and their commentaries. Based upon this request Atisha (whose presentation of the doctrine became later known as the Kadampa tradition) taught what came to be known as the Lam Rim for the Tibetans. Later he was honored very much for this by the Pandits of his original monastery Vikramashila, in India.
The Kadampa monk and student of Milarepa, Gampopa, introduced the Lam Rim to his disciples as a way of developing the mind gradually. Gampopa's work on Lam Rim is known as 'The Jewel Ornament of Liberation: The Wish-Fulfilling Gem of the Noble Teachings' and is studied to this day in the various Kagyu schools of Tibetan Buddhism founded by his disciples.
As Tsongkhapa's Gelug school is derived from and mainly based upon the Kadampa school, it comes to no surprise that Tsongkhapa wrote one of his masterpieces on Lam Rim: 'The Great Treatise on the Stages of the Path of Enlightenment' (Tib. 'Lam Rim Chen Mo') which has about 1000 pages, and is primarily based on literary sources. There is also a medium Lam Rim text by Tsongkhapa (200 pages) and a short one, called 'Lam Rim Dudon' (Tib.), which is often recited daily by Gelugpas and is about 10 pages long.
http://en.wikipedia.org/wiki/Lamrim
Taking a step forward and looking at how Kadampa/Gelugpa school of Tibetan Buddhists defines Larmim, we find following explanation: Lamrim means literally 'the stages of the path' and it is a special arrangement of Buddha's teachings that makes it easy to understand and follow by practitioner.
One might think that at this stage it is all said: Kadampas have their own special arrangement of Buddha's teachings that they follow on their road to the enlightenment, but it is rather far from that!

In fact, there are three schools among Kadampas that could be differentiated by the extent of philosophical study on their paths.
Kadam Shungpawa school studies very extensively and they use as the basis of their doctrine all Je Tsongkhapa's treatises.
Kadam Lamrimpas study less extensively and their basic text for study is Je Tsongkhapa's 'The Great Treatise on the Stages of the Path of Enlightenment' and his 'Middling Exposition of the Stages of the Path'
Kadam Männgagpas study only a few short texts like first Panchen Lama's 'Blissful Path' and the second Panchen Lama's 'Quick Path'.
Thus, Lamrim could mean different things even within one Buddhist school. In next posts I will focus on one of these schools and describe how the practice and study were set up there.