Tare is the deadweight or empty weight of the container. You must take this into account when calculating the maximum authorized load weight of the container, due to country-specific weights per unit. The reason behind this is that there is only a maximum amount of weight per truck allowed on the roads. So if you want to determine how much you can load in a truck in order not to exceed this maximum you will need to take the tare weight of the container into account as well. This is the weight of the container when still empty.