Most residences receive their power from a transformer on a nearby power pole. The output of that transformer is a center-tapped winding. Let's call the output wires "L1","L2", and "neutral" (the center-tap).
The voltage measured from L1 to neutral will be 120 volts. The voltage from L2 to neutral will be 120 volts. The voltage measured from L1 to L2 will be 240 volts.
If the homeowner has an appliance like a clothes dryer which takes a lot of power, the appliance will get its power by connecting between L1 and L2. This delivers the power required at lower current than if the power were delivered using L1 and neutral, for example.
Most home appliances only require 120 volts to operate. Usually the house is wired so that half the house is wired between L1 and neutral. The other half of the circuits are wired between L2 and neutral.
Imagine now that the homeowner has one 120 watt light bulb between L1 and neutral. Further imagine that the homeowner has ten 120 watt light bulbs each wired between L2 and neutral. The current flowing between L1 and neutral would be one amp. The current flowing between L2 and neutral would be ten amps.
If you then disconnect the neutral connection at the pole, the light bulb on L1 would be wired in series with the parallel group of ten light bulbs. The light bulb on L1 has a resistance of 1 ohm. The parallel group of bulbs on L2 has a combined resistance of one tenth of an ohm.
The voltage between L1 and L2 will be divided such that about 90 percent of the voltage, about 216 volts, will appear across the bulb connected to L1. The bulb would glow very brightly for a fraction of a second and then the filament would melt.
First thing I always did when there were strange problems like voltage irregularities or possible current flowing between ground and the line connection was to check for a loose neutral in the panel.