The read command is used to read the telegrams sent you by other countries and by the game, (e.g. when you make a sale or are attacked). When telegrams arrive you are informed with:
You have a new telegram waiting ... if there is just one new one, or You have ten new telegrams waiting ... if there are ten of them, or You have several new telegrams waiting ... if there are very many.
After reading all your telegrams you may discard them by answering yes to the question posed. If you answer no the telegrams will remain pending but you will not be reminded of them.