Biophysics - It means employ physicists to do the job of biology - Okay a joke (partly).
There are certain biologial processes such as protein foilding, protein aggregation and protein structural change occur via coorperative molecular packing and interactions within the complex biological molecule that do not involve in any chemical reaction, and thus not in the realm of biochemistry.
Biophycisicts sometimes require to have the knowledge of mathematical concept and theoretical modelling and only some knowledge of biology in order to carry out studies on topic as mentioned above.
Quite common they also use some intrumentations where results obtain are not as straight forward and need some mathematical analysis skill - such as X-ray crystallography, neutron scattering, protein NMR etc.