"ID+", the default setting, provides more information about the location of the target by attaching depth "strings" showing the digital depth of the target. When there are numerous targets on- screen, not every target depth is shown, to avoid excessive clutter
ID "Off" disables the units interpretation of targets, and displays the "raw" sonar information as it is received. Advanced users may prefer this type of presentation, so they can make there own interpretation from the information displayed.