How does ice work on a locked phone?

Could you please explain to me how ice functions on a locked phone? I'm quite curious about this. Does it somehow unlock the device or does it have a different purpose? Also, how does one apply ice to a locked phone? Is it a specific type of ice or can any kind be used? Could there be any potential risks or damage to the phone by using ice? I'm quite fascinated by this concept and would love to understand it better. Thank you for your time and assistance in clarifying this matter.