The foundation of ALL meditation practice are the two types of meditation that form the core of Buddhist spiritual practice: Tranquillity (Shamatha) meditation which aims at stilling the mind and Insight meditation (Vipasyana) meditation produces insight into the nature of all phenomena. Shamatha and Vipasyana in the Tibetan tradition are different from and more extensive than these meditations of the same name in the Hindu and Theravadin schools. 

The Buddha has said that the achievement of complete happiness--enlightenment or awarening--can only be done by examining one's mind. So first we must begin by calming our mind down so our mind is not continuously interrupted by our discursive thoughts and feelings and emotions. We do no stop our thoughts or feelings because this will only make them stronger, rather we learn through special techniques to reduce our attachment to them so we can experience our mind as it originally was before it became crowded with anxieties, and plans and fears. This is the practice of Shamatha. Then when our mind has calmed down for longer periods of time, we can then "look at" or percieve in a non-conceputal way how our mind has created this entire emeshed samsara that we live it. This is the practice of Vipashyana. 

Tranquility and Insight is a 170 page book Thrangu Rinpoche gives in non-technical language an extensive descriptions of these two kinds of meditation. He includes a discussion of the purpose of these meditations, their different levels of practice, the obstacles and antidotes to these obstacles that can arise, and the accomplishments that can come out of of each practice based on Rinpoche's own practice. As a result this book becomes a careful study of the mind from the point of view of actual meditation practice.