The propeller rotates through the blades in air or water, converting the rotational kinetic energy of the engine into propulsive force. The core principle is Newton's third law - when the blade moves the medium (air or water) backwards, the reaction force of the medium pushes the equipment forward. Taking airplane propellers as an example, when they rotate, the blades form a relative airflow with the air, generating lift and thrust; Marine propellers use propeller blades to divert water and overcome the resistance of the ship's hull. The key to efficiency lies in the matching between blade design (such as pitch, number of blades) and medium characteristics.