Sometimes it is necessary to divide an output signal on several building groups. Also this is realizable with resistors. The calculation of the loss arising inevitably with it, like this webpage shows. Since no coils or capacitors are used, the matching takes place frequency-independently. Attenuators are suitable therby for the wide-band matching.
If you want to know, how looks the equations used into the script, then see at the mathematical background: loss, resistors.