An icebreaker is a special purpose ship or boat designed to move and navigate through ice-covered waters, for a ship to be considered an icebreaker it requires three components: a strengthened hull, an ice-clearing shape, and the power to push through, none of which are possessed by most normal ships.
To pass through ice-covered water, an icebreaker uses its great momentum and power to drive its bow up onto the ice, breaking the ice under the immense weight of the ship. Because a buildup of broken ice in front of a ship can slow it down much more than the breaking of the ice itself, the speed of the ship is increased by having a specially designed hull to direct the broken ice around or under the vessel .
The external components of the ship's propulsion system (propellers, propeller shafts, etc.) are at even greater risk of damage than the vessel's hull, so the ability for an icebreaker to propel itself onto the ice, break it, and successfully clear the debris from its path is essential for its safety.