Here's a breakdown:

* Speed is how fast something is moving. It's a scalar quantity, meaning it only has magnitude (e.g., 50 miles per hour).

* Direction is the way something is moving (e.g., north, south, east, west, or any combination).

* Velocity is the combination of speed and direction. It's a vector quantity, meaning it has both magnitude and direction (e.g., 50 miles per hour north).

Key Points:

* Velocity can be positive or negative depending on the direction of motion. For example, moving east could be positive, while moving west could be negative.

* Constant velocity means the object is moving at a constant speed in a straight line.

* Changing velocity means the object is either speeding up, slowing down, or changing direction.

Examples:

* A car traveling at 60 miles per hour east has a velocity of 60 miles per hour east.

* A ball thrown upwards has a positive velocity as it goes up and a negative velocity as it comes down.

* A satellite orbiting Earth has a constantly changing velocity even if its speed is constant because its direction is constantly changing.

Let me know if you'd like more information on any of these concepts!