What is meditations:

Prayer and contemplation are both exercises in concentration. The normal deluge of conscious thought is restricted, and the mind is brought to one conscious area of operation. The results are those you find in any concentrative practice: deep calm, a physiological slowing of the metabolism and a sense of peace and well-being.

Yogic meditation, which is also purely concentrative. The traditional basic exercises consist of focusing the mind on a single object a stone, a candle flame, a syllable or whatever, and not allowing it to wander. Having acquired the basic skill, the Yogi proceeds to expand his practice by taking on more complex objects of meditation chants, colourful religious images, energy channels in the body and so forth. Still, no matter how complex the object of meditation, the meditation itself remains purely an exercise in concentration. 

In Buddhist tradition, concentration is also highly valued. But a new element is added and more highly stressed. That element is awareness. All Buddhist meditation aims at the development of awareness, using concentration as a tool. The Buddhist tradition is very wide, however, and there are several diverse routes to this goal.

Zen meditation uses two separate tasks. The first is the direct plunge into awareness by sheer force of will. You sit down and you just sit, meaning that you toss out of your mind everything except pure awareness of sitting. This sounds very simple. It is not. A brief trial will demonstrate just how difficult it really is. The second Zen approach used in the Rinzai school is that of tricking the mind out of conscious thought and into pure awareness. This is done by giving the student an unsolvable riddle which he must solve anyway, and by placing him in a horrendous training situation. Since he cannot flee from the pain of the situation, he must flee into a pure experience of the moment. There is nowhere else to go. Zen is tough. It is effective for many people, but it is really tough

Another stratagem, Tantric Buddhism, is nearly the reverse. Conscious thought, at least the way we usually do it, is the manifestation of ego, the you that you usually think that you are. Conscious thought is tightly connected with self-concept. The self-concept or ego is nothing more than a set of reactions and mental images which are artificially pasted to the flowing process of pure awareness. Tantra seeks to obtain pure awareness by destroying this ego image. This is accomplished by a process of visualization. The student is given a particular religious image to meditate upon, for example, one of the deities from the Tantric pantheon. He does this in so thorough a fashion that he becomes that entity. He takes off his own identity and puts on another. This takes a while, as you might imagine, but it works. During the process, he is able to watch the way that the ego is constructed and put in place. He comes to recognize the arbitrary nature of all egos, including his own, and he escapes from bondage to the ego. He is left in a state where he may have an ego if he so chooses, either his own or whichever other he might wish, or he can do without one. Result: pure awareness. Tantra is not exactly a game of patty cake either.