The main difference between a J-trap and a P-trap in Plumbing systems is their shape. A J-trap has a J-shaped bend, while a P-trap has a P-shaped bend. Both traps are used to prevent sewer gases from entering the building, but the shape of the trap can affect how well it functions and how easy it is to clean.
You usually have to unmount it and get at the bottom.
The shape of the drain. A P trap drains out the wall. It looks like a P laid on it's side. An S trap drains in the floor. Again if you laid the S on it's side.
Probably rust and minerals that came loose when you turned the water off and plugged the screen in the spout. Unscrew the screen the the end of the spout and see if that doesn't fix it.