For detailed measurement and calculation information, we have not released public document.
Absolute pressure: when result has to be compared against an external reference, such as get current altitude with sea level pressure from the internet.
Relative Pressure: when the result has to be compared against a previous measurement, such as:
Floor level detection with offset zeroing when entering the building
Height difference between drone and remote control
Noise is a unwanted part of the signal and has to be smaller than the signal that the user wants to measure.