You have two "hot" wires from the electrical service. Each serves
different circuits. Both are needed to provide 220 volts for dryers or
ranges.

You experience is a simple one... and it was easily fixed by the power
company.

The BAD problem is when that THIRD wire fails: The "Neutral wire.

In that case, the 240 volts is distributed across both sets of 120V
loads, and often in a uneven manner, so some devices see less than 120V
and some see more. In many such cases permanent damage is done to some
120V equipment such as TV's etc.

If you EVER see some circuits get brighter and some dimmer, call the
power company at once. Consider running down and shutting the main
break OFF and being without power until it's fixed.

If damage occurs, and it's up on a pole or on the power companies side
of the meter, they can be liable for damages.

I've had this happen. I still have the melted 'souvenier' splice the
power company replaced. Hmm. I did about 10 years ago, wonder where it
is??

Good to keep your eyes open for this unlikely but not that unusual
problem...

Regards, Terry King ...On The Mediterranean in Carthage
(Back ...In The Woods In Vermont for the Summer)