When calibrating displays we are generally working in Video Range levels, which are sometimes referred to as Limited Range, SMPTE Levels, or Legal Levels. These are the levels we anticipate our film, TV and Video content to be displayed in.
Video Levels are defined by their bit values. In a standard 8-bit system (0-255) these levels are from 16-235. When talking about video level patterns that leave the ranges of 0-15 as below black or blacker than black and 236-255 as white/above white.
PC Levels are defined by their bit values, and are also sometimes described as Full Range Levels. In a standard 8-bit system (0-255) these levels are from 0-255. When talking about PC level patterns, the greyscale range will be expanded to completely cover 0-255. This is the default output for most PCs when connected to a PC monitor, but may vary when connected to a video monitor or TV.
Peak White refers to bit level 255, and is also sometimes noted as 109%.
Brightness and Contrast patterns can be used to determine how your video signal is being displayed, as you will be able to see if content above/below Video Levels is being clipped by your display or other devices in the video pipeline.