A differential scope probe is used when a signal cannot be analysed relative to ground. An example of this is the output of a bridged amplifier; neither of the output terminals can be connected to the scope ground, and reading each separately may not be an accurate representation of the signal.
This scope probe is DC coupled, with an input impedance over 1M, and has a relatively low noise floor. A single quad op-amp chip provides input buffers, differential, and has provision to split a single floating supply for dual rail operation. My example is a x100 probe using a 12V plug pack. Input voltage divider resistor values and rail voltages can be changed to suit your needs.