Analog bypass is a feature where the incoming video routed directly to output, sync is still cleaned and separated into H/V.
This setting routes the input signal directly to output when input frequency is higher than about 25kHz.
The intended use is if you want to keep the scaler permanently attached to a monitor, but don't want it do anything for video sources your monitor can handle natively.
Bypass feature is disabled
This is a special case that turns the scaler into a very expensive sync cleaner.