What is the meaning of Stuck between Scylla and Charbdis?

Scylla and Charybdis are greek monsters that dwelled in the strait of messina that ate sailors...Scylla having six heads and twelve feet she would eat men as they passed by her dwelling and Charybdis had one gaping mouth which he would swallow water and belch it out 3 times a day to create whirpools...and so sailors would have to go around the whirlpool yet at the same time avoid Scylla, passing too close to either would mean certain death.

so the saying means basically stuck between two bad things

Basically it means "stuck between a rock and a hard place"