If we observe the mental status that takes place at times when we focus on achieving some objective or other, taking a test, working on a project, running a race, playing music, or creating some work of art, for example, we see that the attention is focused intensely on the task at hand, and there is in most cases, little perception of extraneous sensations or matters, or even of the passage of time. This is concentration. Concentration also applies when the focus is turned toward spiritual development, for instance, through intensive visualisation of a mandala, or through focus on awareness between the eyebrows, or in the heart region, or mindful attention on the breath or on recitation of a particular mantra. Brainwaves in a state of concentration tend to be tightly packed, dense and strong.
Meditation, on the other hand, has a different character when we view the process inwardly. The mental process may be more relaxed, the brainwaves less intense and more widely spaced from each other as the mind moves along its chosen object of meditation. Meditation, by definition, is an inward process, while concentration may be focused either internally or externally.
Each of these processes has its time and place and both clearly can be aids to the spiritual growth of the individual. It may be noted that in his lectures on Raja Yoga, Swami Vivekananda systematically explores the process of achieving concentration and describes the power of concentration and its effects. One-pointed focus is considered to be one of the ultimate achievements of spiritual discipline.
We find that the mind cannot remain constantly in a state of intense concentration. Thus, an alternation with the process of meditation can be highly beneficial and refreshing to the mind. Meditation is more reflective in nature, while concentration is more active.
Sri Aurobindo notes: “Concentration is a gathering together of the consciousness and either centralising at one point or turning on a single object, e.g., the Divine; there can also be a gathered condition throughout the whole being, not at a point. In meditation it is not indispensable to gather like this, one can simply remain with a quiet mind thinking of one subject or observing what comes in the consciousness and dealing with it.”
“Concentration means fixing the consciousness in one place or on one object and in a single condition. Meditation can be diffusive, e.g., thinking about the Divine, receiving impressions and discriminating, watching what goes on in the nature and acting upon it, etc.”
Sri Aurobindo and the Mother, Growing Within: The Psychology of Inner Development, Chapter V Growth of Consciousness, Means and Methods, pp. 89-90