Suppose a block is placed on a horizontal surface. A spring balance is attached to it to apply and measure the applied force.When a horizontal force F is applied,the block does not move. The frictional force becomes F opposing the motion of the body .the static friction is self adjusting force. So,when the applied force is gradually increased ,the force of friction also increases but when the applied force reaches a particular value Fo the body starts moving. Frictional force cannot increase beyond Fo . This is called static friction or limiting friction