The mode (Mo) of a distribution is the value, that is the most frequent in that distribution. In a graphical presentation of a distribution the mode is tha value where the distribution has its maximum.
Sometimes in a distribution there are two or more equally strong classes, making it difficult to decide, where the modal value lies. If, in between two equally strong categories, there is at least one weaker category with less values in it, we call the distribution "bimodal".