This button is to get the scale back to zero. In almost all applications, there is a deadweight placed on the weighing scale. A grocery owner keeps a small pan in which he will weigh the grains before giving them to you. A goldsmith would keep a small dish on his scale in which he will place your ornaments. The weight of that small dish or that pan has to be subtracted from the weight of the actual product that is being weighed. It subtracts that weight.
In short, whenever you press the TARE button on the electronic weighing scale, the scale will come back to zero reading.
The TARE button is also useful when you are preparing a mixture on the weighing scale. Like a Bakery cake or a new color of Paint or mixing various liquids. So let’s say you have to add 20 ml of one liquid to 50 ml of another liquid. First, you pour 20 ml of the first liquid and press TARE. Then you pour 50 ml of another liquid. If there are several liquids to pour, then it is extremely useful.
It is actually used to get the scale to zero when the reading is more than a certain percentage of the maximum weight. So in the previous example of liquids, It will keep on getting the scale to zero till you add the next liquid. When you pick up the container after the final TARE, it will give you the weight of all the liquids and the container.
Some scales have the logic of Nett and Gross Weight on the TARE weight.
The ZERO button is usually on the scale for small hysteresis or creeps variations. This can be a few error divisions.
Many scale merge the two into one function – TARE/ZERO button for simplicity and convenience.