Toilet tank does not fill automatically?

After i flush the toilet, the sound of a toilet refilling in the tank is not there. ihear a little dribble, but not the sound of a tank filling. Nor is there any water in the toilet except a small amount. I life the tank lid and I see at the top of the left contraption dribbling water which makes the dribble sound. This is a long gray neck piece coming out of the bottom of the tank with a black float, it has a hose which runs to and connects to a off whitish plastic center piece in the tank which also stems from the bottom of the tank. To get the sound and the water going again I looked underneath where the water comes from the litte connection to the wall behind the toilet and turned it clockwise until no dribble sound nor actual dribble. All water stopped. I then turned it counterclockwise and it started to fill the tank and stopped when the float piece came up high and I again flushed and it flushded well but then the dribble and the clockwise then the counterclockwise all over again to fill the tank. Why won't the tank fill itself. Why must I now go to the wall connection and turn it clock and then counterclock each time. thank you