Brakes that are in good condition should not squeak and yes it can mean something is wrong that could be dangerous if not checked out and fixed.
Squeaking brakes that continues to squeak when driving down the road or stopping should be checked out because it can mean a lot of different things including anti squeak shims missing or bad.
The brake pads could also be worn and It's very normal for brake pads to begin squealing or scraping when the brake pads wear down to an unsafe level and need replaced.
Brake pads have a little piece of metal on them that makes contact with the rotor and is supposed to make a scraping or squealing sound when the brake pads surface wears down.
If you're noticing a scraping or squealing sound when you press down on the brake pedal to stop the vehicle then it's most likely the wear indicator on the brake pads causing the scraping or squealing noise.
However if the brake pads are squealing or scraping when you're just driving down the road and not depressing the brake pedal then that could indicate some other problem with the brakes which should be checked out just to be safe.