Pressure differences are causing the stop to bounce. This causes temporary water flow in the tank. A new float should take care of this issue.
Loose washer
Depending on which type it is, it either need a new washer or seat in the valve. The washer is a flat rubber disk that seals when you turn the faucet off and the seat is a small rubber cup that does the same thing.
The washer may have become cupped and it has to be opened more to get the same amount of clearance between the washer and the seat.
a washer is generally a rubber washer that tightens and seals as sometimes they will go bad and have to change it..
Proably the faucet has a worn out washer, replacing the washer should fix the problem.
seal to stop water from runing into tank located between tank and bowk
It fills the washer with water from the source, Theres usually a cut-of valve or faucet on the wall near the washer for it.
Washer worn out, washer seat damaged/corroded The most likely reason is that the sealing washer or seat in the tap/faucet is defective.
The washer in the shut off valve has probably split or come off completely over time.
more flow but do not last as long as beveled ===
Supply line clogged. The end of the stem where the washer is may have broken off so that the faucet isn't really opening. Shut the water off and take the stem out of the faucet and see what it looks like.
When you shut the faucet off, the screw pushes a rubber washer against the opening inside the faucet and stops the water. The screw moves in and out in the handle to do this.