Concentration is One directional but Meditation is Multi-directional

It is one of the significant difference between meditation and concentration. You would have noticed that when you concentrate on something, your direction of consciousness points towards that particular thing. For example, if you are concentrating well in reading a book, your whole consciousness would be pointing in the direction of book. You will just remember what you are reading in the book and you will forget about yourself.

In meditation, whatever you are doing, you are aware about the act and also you are aware about the fact that particular act is being done by you. For example, if you are reading a book, you remain aware about what is written in the book. If, you can also remain aware of yourself in those movements then it would not remain concentration but it will become meditation. So, meditation is bi-directional in this context.

We can take another example here. Osho Rajneesh often used to illustrate this example. Concentration is like a torch light whereas, meditation is like a lantern. Torch throws light in one direction but lantern does not throw light in one direction.

We can notice from the above examples that during concentration we can have thoughts. You are reading a book then you can also think about the matter present in the book. It is without being aware of yourself. In meditation when you do anything, you are aware about the act and yourself. So, there is no space for thoughts. Thoughts can only be there if the arrow of awareness which points towards you is not there any more. When we are thinking about anything, it can also become meditation but only if you are aware that thoughts are being thought by you.