Flex plate is used on an automatic transmission car. The plate bolts to the crankshaft and the plate has 4 mounting holes where the transmisson torque converter bolts to the flexplate. The ring gear is welded to the converter and the starter drives the ring gear to crank the engine.
On a manual shift car you have a flywheel that is bolted to the crankshaft. The flywheel has the ring gear mounted on it.
It is kind of common to have the torque converter to flex plate mounting bolts back out and make noises as they rub/hit on items such as the back of the block or starter.