(Simplified) A ground wire (equipment grounding conductor) may be run separately from the outlet in question to the panel holding the breaker for that branch circuit, exactly, approximately, or vaguely following the path of the circuit conductors. Should this new EGC first reach a fat ground wire (grounding electrode conductor) from a panel out to a ground rod or water pipe, it may end and be clamped on there. New: If the new EGC first reaches a properly grounded outlet of at least the same amperage (a 10 gauge EGC reaching a 20 amp 12 gauge circuit does not qualify) it may also be connected to the existing EGC there. The new EGC is installed in the same manner and with the same physical protection as a new branch circuit might be installed in the same locations.
The zero reference for household voltages is the center tap of the pole transformer. For almost all homes in the U.S. the neutral wire to the home is the same wire as the ground wire from pole to home (which for overhead service drops is also the support wire called a messenger wire).
Which means that, unless there is a defect, the main panel (where the first whole house disconnect is/should be) neutral bus bar is zero reference for the home. At the main panel the neutral bus bar is/should be bonded to the panel back thus making the ground bus bar and anything attached to that also at zero volts.
Since one of the purposes of equipment grounding conductors is to shut off the breaker should exposed parts such as the dryer shell become energized, there can be a brief moment where voltage drop results in the voltage to zero reference at the far end of the EGC becoming non-zero, as described earlier.
Fault -- An unwanted touching of wires or metal parts that can result in abnormal current flows (fault current).
Bond -- An essentially resistance free electrical connection that is not a fault, in the sense that if A is bonded to B and B is bonded to C then A is bonded to C.
Short circuit or short -- Connection, usually but not always undesirable, resulting in current "taking a short cut," not flowing through a load (light, appliance, etc.) or device that said current normally flows through.