Speed is the distance an object travels each unit of time. Velocity is almost the same as speed, but also takes in account of the direction of the object. Two bodies moving closer together, at the same speed, have twice the velocity relative to each other.
Objects stay the same velocity until a force is applied to it. Drag/air resistance and friction always halt the object, but only until forces are constantly applied. Bodies in vacuums always move, and don’t need forces.
Acceleration is getting faster, such as a car accelerating. The car is using more thrust, which is more than the opposing force(s). Larger forces make a larger acceleration than smaller ones. Deceleration is the opposite.
The reason an object continues to move is because of momentum. Momentum is mass multiplied by velocity. To stop a moving object, you have to remove the momentum, which needs energy through a force. Momentum at zero means the object has stopped moving and is stationary. Just remember, energy is not created or destroyed, and the momentum has just been transferred to the thing which delivered the force which stopped the object.