Sri Chinmoy: When we concentrate, we focus all our attention on a particular object or subject. Concentration is one-pointed attention, focusing on the tiniest particle. When we concentrate, we do not have the need to have any thought inside the mind. We want to run the fastest, like a deer; we want only to reach our goal. When we meditate, we want to see the vastness, not only inside our mind but also inside our entire being. We meditate in order to feel within ourselves the vastness of the sky, the ocean.
So, we can say that concentration deals with the smallest reality and meditation deals with the largest reality. But both realities are equally important at a particular stage of our evolution. Concentration paves the way for proper meditation. Suppose right now I want to meditate but there are thousands of ideas entering into my mind. How am I going to meditate? If I want to meditate with these thoughts, then I will never get any peace of mind or vastness inside of me. In the spiritual life there are three stages. Concentration is the first stage, then comes meditation and finally contemplation.