Communication is important to management because managers must understand orders that come from above them and transmit them effectively to those below. They must also gather information from below and transmit it to those above. In both cases, the process must be done in a way that ensures that management understands the information being given to it and transmits it in a clear and helpful way.
Managers are the middle level of any corporation. They must communicate with the upper levels of the company so as to understand what the upper levels want. They must then transmit the orders to the lower levels. When they do so, they must communicate effectively and in a personable way so that the lower-level employees will understand what is needed and will be motivated to try to comply. Managers must also listen (this is part of communication) to their subordinates. At times, information gathered from the subordinates must be transmitted to higher levels in the company. Again, this must be done clearly and in such a way that the manager's superiors do not feel put off by the suggestions from their subordinates.
For these reasons, communication is extremely important to management.