Does an electronic balance measure mass or weight?

Scales can only “measure” weight. Some scales will try to convert it to mass for you.
The difference between mass and weight is that weight is the downward force exerted as a result of gravity pulling on an objects mass. Mass is the measure of the amount of matter in an object. Mass never changes but weight may change depending upon location.
Your scale may run a simple program to give you the approximate mass however you have to realize that the mass it gives is likely incorrect. Unless your balance measures the strength of the gravitational field at its location on earth it will always assume that the due to gravity is 9.81 m/ss. This is not the case for every location on earth, the gravitational field is not evenly distributed, therefore your scale likely cannot display mass with precision.
It can however tell you the exact WEIGHT of an object where it is located. You can use weight to calculate a more precise mass using other instruments to measure the acceleration due to gravity at your current location.
In short an electronic balance can be calibrated to tell you both mass and weight, but you should probably assume that the mass value is not as precise as the weight.