There is a friction force of 10 Newtons between a box and a table top. In order to move that box at constant velocity, you would have to supply a force.

To move the box at constant velocity, the applied force must exactly balance the friction force (10 N). When velocity is constant, acceleration is zero, so net force must be zero according to Newton's second law (F=ma). If you applied slightly more than 10 N, the box would accelerate. Slightly less than 10 N wouldn't overcome friction. Exactly 10 N makes net force zero, maintaining constant velocity.