Say you have a 0V and 24V power input, but you need a bipolar power supply, or maybe a part of your circuitry powered with its 0V offset from the power input 0V?

Using linear voltage regulators

You can use voltage regulators to create voltage rails wherever you like within your power input voltage range. But bear in mind that positive linear voltage regulators source current and you need to use negative linear voltage regulators to be able to sink current (i.e. for a new 0V rail).

For example, you have 0V and +24V power input and will be exciting a load cell at +15V, but your load cell amplifier has an analog input voltage range of 0 to 5V. To deal with the load cell differential voltage signal coming in centered at 7.5V (15V / 2) you need the IC that measures it to have its GND at say +5V and its VCC at say +10V, referenced to the real 0V power input rail. The IC will see a +5V supply, but actually it’s lifted 5V off your real 0V rail.

A good low-noise solution would be to create the +10V rail using a linear reg as normal, then a -5V rail off that using another linear reg, but using a negative voltage regulator that will sink current.

Charge pump

Devices like the LM27762 can create and adjustable +-1.5V to +-5V from 2.7 to 5.5V.