The escape velocity of a planet refers to the minimum velocity an object needs to achieve in order to break free from the gravitational pull of that planet and escape into space. It is the speed required for an object to overcome the planet's gravitational attraction and move away indefinitely, without falling back.

Escape velocity depends on the mass and radius of the planet. The greater the mass of the planet, the stronger its gravitational pull, requiring a higher escape velocity. Similarly, a larger planet with a larger radius will also have a higher escape velocity.

Escape velocity is an essential concept in space exploration and satellite launches. For example, when launching a spacecraft from Earth, it needs to reach a velocity of approximately 11.2 kilometers per second (km/s) to overcome Earth's gravitational pull and enter orbit around the planet or continue on a trajectory to another celestial body.

Each planet in our solar system has its own unique escape velocity. For instance, Mercury, the closest planet to the Sun, has a relatively low escape velocity of about 4.3 km/s. On the other hand, gas giants like Jupiter and Saturn have much higher escape velocities, around 59.5 km/s and 35.5 km/s, respectively. The escape velocity of a planet determines the energy and speed required for spacecraft to explore or leave its vicinity.