The Depth Gauge is the tiny rounded hump on each link in front of the cutter blade.
The thickness of your saw’s cut can be identified by measuring the distance between the depth gauge and the leading edge of the cutting blade.
These should be maintained on a regular basis. If your chain begins to jump rather than smoothly running around the bar, it often means the depth gauge should be lowered.
Generally it is good practise to adjust the depth gauge every other time or so that you sharpen the chain.