A garbage disposal humming but not working is getting power to the motor, but the flywheel cannot turn. Usually something is jammed between the impellers and the grinding ring, such as a bone, fruit pit or utensil. Less often, the bearings have seized or the motor itself is failing, which no amount of unjamming will fix. Turkey bones are a common holiday cause; see what can’t go down the disposal on Thanksgiving.
Switch the disposal off right away, because a stalled motor overheats. Then unplug it under the sink or turn off its breaker, and never put a hand inside the unit. Look for a small hex socket in the center of the bottom. Fit the wrench that came with the disposal, or a 1/4-inch Allen wrench, and work it back and forth until it turns freely in full circles, as the manufacturer’s jammed disposal instructions describe. Shine a flashlight into the chamber and lift out anything loose with tongs or pliers.
Next, press the red reset button on the bottom. It pops out when the motor overheats, and if it will not stay in, wait ten minutes and try again. Restore power, run cold water, then switch the disposal on. If it jams again, repeat the wrench step, since a stubborn jam can take several tries.
One honest limit: these steps only help when something is stuck. If the wrench turns freely and the unit still hums after a reset, the motor or its bearings have most likely failed, and the practical fix is a new unit, covered in how to replace a garbage disposal. If water still stands in the sink once the disposal spins, the blockage is in the drain line below it, and that calls for drain cleaning rather than more grinding.