A case of constipation usually means that you've had one or fewer bowel-movements in a typical day. This might happen because you've just changed your diet from bad food to good food. Your body has to adjust to the different food, so you have to give your body time to get used to it.
Another common cause for constipation is dehydration. If you don/t take in the proper amount of water every day, you will have trouble with your colon being unable to push waste out.